This would have been a great April Fools joke one year, but it's real now. I've turned it off on every site that offers it (Xanga back when I actually used it--I think that's the only one) because IP addresses are less personal than usernames. Remember, all you need to stalk someone these days is an email address!
LJ Toys, looks like you'll still have business. Just not mine.
I wonder if you can turn this on for communities. That could have some interesting consequences.