....most relied on 3G, and assumed they'd be easily able to exploit it on an (almost) ubiquitous basis.
I don't think that assumption bears closer scrutiny:
- 3G outdoor coverage is getting better, but is still hardly ubiquitous. Many operators' rollout schedules are determined by the strict terms of their spectrum licence - and some are complying with the letter, but not the spirit of the law. So yes, notionally, there is "coverage"... but whether it will support real-world applications is another matter. How much capacity is actually available, either at the air interface, or the backhaul to the rest of the network?
- Backhaul, more generally, is an issue. Even in the well-engineered & genuinely aggresive bits of operator 3G-land, it's not uncommon to have a total backhaul availability of 4-6Mbit/s - not great if you've got lots of concurrent users in a confined area.
- Indoor 3G coverage is somewhere between patchy and non-existent. Until other operators start copying DoCoMo's great idea & citing in-building systems in their financial reports & KPIs, don't expect to sell applications people mostly tend to use at home, in the office, or in many retail or transportation environments. (Amusing side-note - one of the mobile TV trials found that the most popular place to watch was in the loo.... which is fine, until you realise it's at least 2 walls away from outdoor coverage)
- Just because someone has a 3G phone, don't assume they actually connect to a 3G network. I've written before about the (proactive on my part) struggle I had to get a 3G SIM to replace my 2G one. And recently, I switched off 3G on my main phone because of a network glitch, locking it to 2G. After 2 days, I realised I'd forgotten to switch back - I remembered when I saw the power meter hadn't moved. So I've left it on 2G most of the time, and my battery now lasts 3x longer between charges. On balance, losing always-on 3G services seems a small price to pay.
- Much of the world relies on prepay billing (between 50-80% of subscribers in most European countries, for example). This % rises among key target groups like teenagers. There are not many 3G prepay deals around, nor many 3G MVNOs. (Generally 3G phones are expensive & hence subsidised - but not many operators like to subsidise prepay phones as they risk them being "unlocked" and used with competitors' services). I certainly don't think I've seen 3G SIMs being sold separately anywhere - imagine the confusion that would ensue in those markets where people routinely buy phone+SIM separately, often from non-mobile specialist shops.
- Because most 3G phones are sold through operator-controlled channels, many have customised software stacks. As a 3rd-party application vendor, you cannot assume all Nokia XXXX or Motorola YYYY handsets have the same capabilities & functions. Some may be locked to 3rd-party applications, others may have custom music / video / security software. Sure, some high-end devices are sold "vanilla", but these are rare.
- Roaming. A separate set of nightmares I'm not going to expand on here - but I'm sure you get the idea.
None of the above will be fixed quickly. Indoor coverage, in particular, will still be lousy 5 years hence, in most countries.
Consequently, most 3G services will also need to work in 2.5G coverage. And in order to give a good user experience, you really ought to warn the customer to expect slower service, more latency and so on - especially if it flips to 2.5G in the middle of doing something. When my mobile video suddenly drops in quality, or my download slows (assuming handover works OK) - what did I get charged? Did something pop up on screen to keep me posted on what happened? Did the application recognise the shift and change streaming speed or codec?
Bottom line - do lots of testing, in lots of real-world places, and see if you'd be happy with the overall user experience working across both 3G and 2.5G....