My worry is that we'll schedule a blockchain split 6 months from now, and between now and then somebody implements a secure, way-cool, everybody-decides-to-use, way to use your email address as a bitcoin address.
So my receiving address is 'gavinandresen@gmail.com' and suddenly all the arguing over length of the bitcoin addresses used behind the scenes was just a huge waste of time.
I'm as guilty of doing stuff like that as the next geek-- I can get so focused on one little bit of a problem I don't even realize solving a larger problem makes the whole issue go away. Slap me upside the head if you see me going down that path...