what would happen to your online profile(s)?

i was thinking about this a couple of weeks ago.

i have:
myspace
facebook
dis
a couple of band/music based forums
gmail
hotmail*6
yahoo
last.fm

so whats going to happen to these once i die?
i'm sure that no-one knows my passwords and i doubt my parents would know/care about any of these accounts. so theyre just going to hang there, in the void of cyberspace.
worried?

what about your 'online existance'? will it survive past your death?