Once upon a time, someone decided that the train service from London to Birmingham was terrible, and that a bus service would be much better. So they started a bus company. However, once they were up and running, they found that it would be much more efficient if they built big bus stations in the centre of each city. And to get the loading to work better, you want to get 8-10 buses linked together as one vehicle. And then you really need to raise money and build a dedicated road from London to Birmingham...
The point is, buses can be much more flexible or efficient than trains, but you need to be careful you're not actually planning to build a train after all. Are you trying to unbundle an existing product with a more flexible tech that allows a more flexible product - which is where buses beat trains - or to replicate it?
This is a recurrent problem in mobile - there are wireless technologies around that look like they should be able to disrupt cellular operators, but actually they never do, because to disrupt cellular you need another train line, not a bus.
Mobile LOOKS like a tech business where tech should change things, but most of the money in a new mobile network goes on base stations and three quarters of the cost of an urban base station is in the construction and site acquisition, not the equipment (the cost of a national fibre network, meanwhile, is irrelevant). And the number of towers you need to get enough coverage for the first customer to sign up has relatively little to do with the technology you use - it's down to the physics of in-building penetration at the frequency you're using and the number of hills and mountains there are. (Technology has a big effect on the number of towers you need to build later for capacity, of course, but not for coverage.)
Hence the problem with disrupting mobile networks with new radical technology: the notional efficiency gain tends to get buried by the rest of the underlying economics of the system, all of which you need to build just the same.
Hence, for example, the now totally failed attempts to use WiMax for mobile service were a bit like replacing diesel engines with electric: you might or might not choose to do it if you were building a national train system from scratch, but the real money would be going on tracks regardless. The same applies to wifi, which in which the bus v train analogue is almost perfect - wifi is great, but if you try to use it to offer a mobile service you end up building, well, a mobile network, with no cost savings at all and, in fact, a much less efficient business than you'd get if you'd started with the right technology in the first place.
Of course, none of this is to say that you can't disrupt the mobile network industry in any given country. But you do it by being a mobile operator - by getting spectrum, and building towers, and (very often) by getting the regulator to put a hefty thumb on the competitive scales in your favour.
As an aside, one of the things that dropped out of the great MVNO bubble of 7-8 years ago is that a reseller can't disrupt the person whose infrastructure they're reselling - unless, again, the regulator imposes disruptive wholesale rates or the telco screws up and sets the prices too low (as One2One/T-Mobile did for Virgin Mobile in the UK), or just uses MVNOs to fight a price war by proxy (which I don't think really counts as disruption). MVNOs need an angle, whether that's being a supermarket, or targeting immigrants, or something else - just being an MVNO isn't enough.
The place in which technology really IS affecting mobile network operators, of course, is in what goes over the top - WhatsApp versus SMS, with voice coming next. Unlike a pure infrastructure play, these are essentially unbundling stories, and they’re aiming unbundling at the right part of the system. Of course, that's not how a telco sees them - a telco sees them as arbitrage.
The classic telco arbitrage story was long distance and international. Long-distance and international connections used to be very expensive, no longer are, but telcos pricing had not fallen to match, and first calling cards and then Skype arbitraged the difference between the list price and the real economics of long-distance or sub-sea fibre. Mobile messaging apps do something similar for data, arbitraging the gap between the economic cost of a few K of data and the price charged for SMS. As cellular data speeds go up, we should expect voice apps to take off in a big way as well: the pricing gap is not as big but things like on-net/off-net call pricing will also go away (with both positive and negative margin effects for telco, for reasons I won't go into here).
(Incidentally, VOIP annoys mobile operators on principle since it tends to use several times more radio network capacity than a circuit-switched call, as it's not optimised for how the network functions (this will change with LTE). Hence VOIP on cellular is an interesting example of new technology that actually has worse real underlying economics than the product it attacks.)
How much does this matter to mobile operators, though? There's also another train analogy that's applicable here: Roald Dahl wrote a story about a character who made a living by arbitraging railway luggage fees. He had noticed that, while you had to pay the railway a luggage fee based on what your luggage weighed, if the scales showed a negative number then the railway company had to pay you. So he travelled everywhere with a large suitcase full of helium and charged the railway company a fee.
The idea that OTT messaging services pose some sort of existential threat to telcos remind me a lot of this story. If the railway company can't change the pricing system and everyone goes out and buys a helium suitcase then yes, they're screwed. But telcos can and do change their prices. And that helium suitcase doesn't somehow change the cost of coal or locomotives. You're not using innovation to uncover a new set of economics - you're just hacking the pricing plan.
Hence, the challenge for mobile operators is to change their tariffs. WhatsApp and Facebook Messenger do not change what it costs to provide you with a pipe. If the technology now means that the pricing scheme is no longer aligned with the economic cost of the network, you need to change the pricing scheme.
There are two problems in this, though. The first is that repricing a business whose main competitive dynamic is complex and highly-wrought pricing schemes is a nightmare. In the short-term churn will shoot up and in the long-term moving to unlimited bundles means you cap the ARPU from your whales - all those people currently paying €200/month for voice calls will drop down to your €50 unlimited plan. You may well end up with a lower ARPU than before. The second is that if you have less freedom to offer complex pricing schemes you face the risk that the market will move to much more commoditised, easily comparable pricing, with a consequently much higher likelihood of price wars. Both of these issues are essentially transitional, and will vary a lot by country - in some places the transition will be fairly smooth and in others it’ll be painful and result in a step change downwards in ARPU. The arrival of data bundles is a great example - US operators added them to people's plans, pushing ARPU up, but European operators weren't able to get away with a price increase because the markets were much more competitive. The end of separate SMS pricing will see similar differences.
The big problem that these products pose to MNOs, it seems to me, is not actually the threat to SMS revenue. Rather, it’s the threat to identity. We do already have number portability, but changing your number remains a major frictional issue reducing churn. But if your contact point moves to FB Messenger or some yet-to-be-founded app that explodes in the next few years, then the SIM you have in your phone today doesn’t matter at all, and you could swap it in and out from week to week depending on which mobile operator was offering the best deal - a great recipe for truly murderous price wars. For a really killer effect, of course, you’d have to combine that with an end to the subsidy + contract model, which is far from certain (and would also be terrible for Apple and Samsung). But that’s the threat.