For now, that all depends on which sites you use. Social-networking sites tend to keep accounts up. Facebook's memorialized profiles are restricted to the user's friends, who can continue posting comments; relatives may request to have a profile removed altogether. (They cannot, however, gain access, which means users' private messages are kept as just that.) Rival MySpace has adopted a similar policy, but does not restrict viewing, which has inspired one man to create MyDeathSpace.com, which aggregates profiles of the deceased. LiveJournal, one of the first blog providers, has an informal policy of freezing accounts but keeping them online. Photo-storage site Flickr, too, keeps accounts up; if any photos were tagged as private, however, Flickr won't let friends or family into the account to access them.
Same article in Vietnamese
Spain (I think)