Sony has filed a very interesting patent in the US for some "vehicle communication equipment" where you can push some buttons in your car and beam a message over to another car nearby that has the same widget installed. Apart from messages like "you cut me off mofo!" and "hey lady you're hawt, pull over" coming into frequent use, my money is on these devices being spammed as soon as a large enough portion of cars have them installed.
Just think, years from now college kids can have cruising and beaming messages to cars as their intern gig, rather than web surfing and spamming myspace and xanga. Now that's progress!