I use my Hotmail account as a spam trainer for my bayesian email filtering program. Nobody else emails me at that account, and chances are new flavors and styles of spam will land at Hotmail first, loading up my spam database to protect my other accounts. In fact, through the magic of a POP3 to HTTP proxy for Hotmail, I don't think I've actually logged in to check my Hotmail in months. It's like my own personal spam factory.