Absolutely retarded. I've noticed that regarding auction sites like Ubid (which used to be a great place years ago). Morons will bid way too much for crap when they could have just bought it new. I am glad to see them waste their money because they didn't do their research on it.
Like Anubis said only if it's a rare processor they may need for some reason and can't get it anywhere else or they can get it slightly cheaper on Ebay.
Overall it's pretty subjective but I can guage its worth it depending on the situation when I buy them refurbed at Newegg, for instance. I got my Athlon XP 2500+ OEM which was selling for about $100.00 at the time for $60.00. To me that was a good deal. Same thing with an XP 1700+ I got for $30.00 when they were selling for about $52.00 new OEM.
Edit: Just remembered 2500+ wasn't OEM...came with HSF.