said by fatness:A lot of good (and some bad) information would disappear from the site if this were allowed. In particular, posters who got pressured from a past or current employer would remove information at that employer's request. Posters who are job hunting would remove some of their old posts here, concerned that it might somehow affect their future employment with someone. Posters who want to scrub google results of their posts would remove things they've posted. Finally, posters who get ticked off momentarily would remove a significant amount of posts.
It has always seemed a bad idea to me for those reasons.
And for true "I wish I hadn't posted that" moments, the Edit function is there for a day or 2 to go in and edit what you posted. Of course, it would be nice if that edit was then reflected in those who replied to the post using quoted sections.