A lot of old threads are no longer relevant. Either the poster has moved on from the situation or is no longer on the site. It's really to reduce clutter and reduce the amount of really old threads that pop up.
I should probably add that the message which displays isn't something we have typed up. I'm not sure what the general thought process was behind it, but that 4th sentence in particular just sounds a tad too threatening and menacing for my liking. :-/ I'll see if I can get that changed to something more useful which incorporates Brad's points, rather than threatens to put a horse's head in your bed while you sleep.
