The phenomena, known as “The Clbuttic Mistake” after a mangling of the word “classic” that is believed to be the first identified instance of the problem, can be found on tens of thousands of websites.
The error is caused by poorly programmed anti-obscenity filters – similar to spell checkers – that automatically replace words considered rude or offensive with more acceptable variants. “Butt” replaces “ass”, “breast” is substituted for “tit”, and so on.
We've written about this phenomenon previously, so I'm just pbutting this on as a followup for your consideration.
Via Language Log, which rather undercuts the Daily Telegraph's thesis, but the story is so amusing you should read it anyway. (And yes, I know that the caption on this post doesn't quite fit.)