It's worth mentioning that the LiveJournal is open source, so people who complain about the poor service but still want the same functionality can, if they are technically savvy enough, run their own clone of the system.
However, the main attraction to LiveJournal for many people is the large user base and the friends list feature. The former merely means there are a lot of people already writing there, so there's a lot of people to read and interact with, especially since LiveJournal lets you comment on posts that people have made. The latter makes it easy to read a a set of people's journals. Certainly, the user base can't be duplicated just by running your own site, which means starting my own LiveJournal system is an incomplete solution at best.