In short what we are talking about is bandwidth. Currently the fastest theoretical download speed in the UK is 7.2Mbit HSDPA. For those with poor home broadband connections this may sound extremely fast, but the issue is a) this speed is never reached in reality, and b) it is split between every user currently accessing it at the base station (local distribution point) of their particular network. It only takes one user to start streaming YouTube clips or uploading pictures to Facebook or Twitter to bring everything to a standstill.
Worse still, unlike coverage, there is no single body that can be blamed. Carriers try to fit as many base stations as possible (there are 10s of 1000s across the UK), but the UK is one of the most densely populated countries in the world. Meanwhile smartphones are bought in ever greater quantities and their apps consume ever more data. The irony shouldn't be lost that the greatest of them all is the BBC's own iPlayer web app.
So the obvious solution is more bandwidth at each base station. This can be done through LTE (Long Term Evolution), the final iteration of 3G data services (technically it is 3.9G, but will be marketed as 4G). LTE bumps base station bandwidth from a maximum of 7.2Mbit to a whopping 160Mbit and that is only in its first iteration. It can scale to 300Mbit using only software updates. Better still LTE is a real world technology which has already rolled out in many countries around the world with LTE dongles and compatible handsets, such as the HTC Evo 4G (below) widely available.
Carriers are moving too. O2 was the first carrier to deploy an LTE trial in the UK way back in 2009, while in May BT and Everything Everywhere announced their LTE trials will start in September. So we have reason to celebrate? Not yet.
There are two primary reasons why. Firstly the carriers don't yet own the spectrum required to distribute LTE. In fact Ofcom only began its consultation process into how best to sell off the licences in March. Secondly carriers themselves aren't as motivated as they were to launch 3G. This is because the astronomical sums they paid for the 3G spectrum at the start of the decade have still yet to be recouped and cash reserves set aside for LTE bidding are much lower.
So what does the future hold? Until there is widespread distribution of LTE (unlikely before 2013-2014), the continued proliferation of smartphones and their increasingly data heavy services mean the situation will only get worse. Congestion will continue to affect both voice and data services (regardless of coverage or signal strength) and the UK will fall behind leading nations, having previously been near the forefront of mobile development.
The good news is the situation will eventually resolve itself. The bad news is many continue to look for solutions by asking the wrong questions.