what the hell?

Lately while stalking some Xanga's I notice that people like to delete some of their posts and pretend they didn't exist (As if a million Xanga posts and comments cried out in terror and were silenced). What's up with that, why do people purposely delete their posts? I hope they at least keep a copy of it somewhere for reference later on when they can say, "Yeah I wrote that and that's how I was feeling at that time"