AT&T has been increasingly dependant on wi-fi to offload some of their data hogs from their cellular network. At the Mobile Summit in Spain, T-Mobile admits the same thing. T-Mobile initially established their HotSpot service to gain a marketing advantage with home cell-sites they could charge us for. AT&T, Sprint and Verizon Wireless were trying to grow their offerings with a "femtocell' (micro-sized cell sites) at a monthly fee. We were an early advocate of buying your own Femtocell without the monthly charge. My how things have changed.
Now instead of the carriers trying to 'help' you with better coverage, they're helping themselves by offering more handsets that can make calls whether you're on their cellular network or wi-fi, some can exchange each type of network seamlessly. To that end, AT&T has also been building more wi-fi hotspots. You might call this the 'iPhone Effect.' Too much data demand has actually given us more coverage, even if it's in our own home.
On a related note, Alcatel-Lucent introduced at the same conference a cell site and antenna the size and shape of a rubic's cube. The idea is cell sites no longer need to be on top of tall towers, they can be just above our head. How about "More bars in more bars!"