Twitter is great for a lot of things, but I think my favorite use of it is public smack-talking. Just read what Lance Armstrong has to say about his Tour de France-winning teammate, Alberto Contador. And in the tech world, we have some good smack talking from Verizon directed at rival AT&T today. John Czwartacki, who is the policy blog editor for Verizon, sent the following public message on Twitter, " This what USA's most reliable wireless network sends BEFORE a conference. #VDC "— complete with a TwitPic (below) of a giant Verizon truck parked outside the conference to bolster signal.