I experimented somewhat with this right when we moved into our house before we were hooked up. I borrowed an outrageous ~4ft antenna from my dad (who used it for a similar purpose when he first moved into his apartment last year, stealing open wifi from a nearby church). I found no fewer than 62 networks including a hotel a few streets over (this was with the antenna indoors on a second story, rotated according to "tune in", as it was very directional). It can definitely be done. The best part are the funny wifi hotspot names. My favorite one was "Bill Wi The Science Fi." Mine right now is "FBI Surveillance Van #42."
WEP can be cracked quite easily in a matter of minutes, which I found out when I was ...doing that for educational purposes with permission.