The trouble there is that you're pretty much stuck with 2.4GHz, 5GHz, or 600-900MHz. Most everything in between is privately owned, and forbidden from use by the public. 600-900MHz can provide something like 2-5mbps per connection, and is able to penetrate many obstructions (except hills and thick forest). 2.4GHz can provide speeds comparable to ADSL, but it can't penetrate trees. There is probably an ideal compromise frequency, but since it's privately-owned, we'll probably never know.
Since in the 2-5mbps (600-900MHz) range, you have to either beam multiple connections to one house for ADSL speeds, this is extremely cost-inefficient. 2.4GHz is more promising, but it really only works in flat farmland which has been cleared of trees. Desert is another fantastic place where 2.4GHz and even 5GHz signals could live, but unfortunately, I'm in a forested area.
However, there's still some hope of existing in the Digital Age without ADSL, and it comes in the form of balloons, which is why Google's recently-announced foray into this sector is extremely important. Balloons can fly high in the air (but not crazy-far-out like satellites) and broadcast a 2.4GHz or 5GHz signal without nearly as much signal penetration issue (since the signal is more vertical than horizontal in a high-up balloon -- towers are very tall because they're trying to avoid having to go through a bunch of terrestrial obstructions, but this isn't particularly effective since it's very costly to build them high enough to be more likely to send a signal somewhere and have it be at a vertical-enough angle where it's not having to deal with a bunch of trees and hills). Balloons may or may not be the holy grail in getting higher-frequency signals from central locations to a home without costly landlines.
Well-designed solar balloons may be able to stay in the skies for months or even years, but there's an issue in having the balloon not blow far away. It may be possible to solve this with complex tethering (I'd consider this a kludgey solution, though I think it likely to be the most cost-effective if you hold enough land for it not to blow into others' land). Google's taking a different route, trying to control the balloon's location through active propellants, more like a spacecraft. The balloons would be equipped with a computer which keeps track of its GPS position, and appropriately engages thrust when it goes off-course. If their experiments prove successful, the era of towers may be near its end, replaced with high-flying routers and satellites. (This'd be extra-super cool if technicians maintained these by floating up to the balloon [or in the tethered solution, by scaling the rope], instead of bringing the balloon down to them)
ETA: I thought about scaling high-guage fishing wire tethers a little bit more. That wouldn't be awesome. That would suck.