Just a little background for those who may not know: Once you hit the ol' "Submit Reply" button, you have a limited amount of time to "delete" a post, at least from the perspective of the post being visible to the average forum participant. However, those who have access to the forum program's administrative controls, such as the webmaster and the moderators, can still see the deleted post - forever.

The most common reason is that I might reconsider a post as either going too far from a TOU perspective, or from my own personal perspective, and kill it for that reason.

Sometimes it is from a perspective of not leaving tracks, as I might relate some personal event or memory and later feel uncomfortable doing so.

I can recall one recent instance - at one point I thought that the OP was ignoring my posts because I was needling an acquaintance of his on other threads, so I said eff it and tried to erase my participation on that particular thread. Later I realized that I was mistaken in my beliefs.