I live in a nice neighborhood, in an affluent community in Northern Virginia, surrounded by other dotcommers and tech workers. Starbucks is pretty close by, as is Home Depot, the firehouse, and a little company called AOL. There is so much fiber in the hill in front of my home that I fear the day that it's lit up the hill will explode and we'll all go blind from the bright light (fiber geeks: I know fibre doesn't leak light, I'm making a joke). A T-1 can be installed at my home from $600/month, however NO OTHER FORM OF BROADBAND IS AVAILABLE. Crazy.
Verizon is testing a fixed, non-line-of-site wireless system in my area. The transmitters are said to be very much like the large flat PCS/cellular antennas spread across the country. Seeing as there are only a few of them in existence, they can't be as cheap as a PCS antenna. So, consider your cell phone and its reception capabilities, especially if you live in the Suburban/rural borderlands. Not always perfect right?
Now, imagine the cost of outfitting every cell tower in the nation with fixed wireless antenna. This won't happen over night, even if Verizon's trials go very well. The holes in the WiFi blanket will outnumber the coverage areas for years to come, making Warchalking more useful than less useful for a good long time.