I honestly thought that if I ever kept an online journal again, I'd keep it on my own site so I could keep track of who was visiting my journal to some degree.  And I might password protect it, etc.  Or do it as an email list.
And I wasn't sure what to make of the many journal sites out there.
But I really really like the site and software that the folks at LiveJournal have put together.  I got hooked 'cuz some friends had journals there and now more friends have journals there and well.  Now I have a journal there, too.  
You can also write weblogs there, too.  The standalone livejournal clients are spiffy, lots of things about the site are spiffy.