Do this: Make yourself a list of EVERYTHING you have a username/password for on the internet. Now, cross out the things that are required by your job (school district or college email account for example). Do the same for credit, cellphone, bank accounts that you can access online.
Okay, what's that leave you with?
Probably your social-networking sites, MySpace, Twitter, Facebook, Flickr, etc. as well as any blogs, games, or cloudware sites you use. Take a look at how many of your social-networking sites overlap. It's the same problem I faced with instant messaging. I was an avid ICQ user until college, when most of my new friends were already hooked into AIM. Then came Second Life where all my friends were Yahoo users. Pidgin came around and let me combine them all into a single app, thankfully.
I don't know if it would work for social-networking sites, though. Twitter happens to be my favorite
site right now for it's ease of use, and constant connectivity. There's of course, Jaiku, Pownce, and many others that all provide similar products (and I have accounts with them all...).
So the question is, "How much is too much?" Do the web2.0 pioneers just keep gathering accounts, or do we draw the line somewhere asking ourselves if we really need something new? I don't know if I'd stop "collecting" accounts, but I've definitely limited myself to using the ones that truly do my a service of making life easier. Leave thoughts!