I visit John Battelle's Searchblog daily and it hurts me to see the amount of spam that is submitted through his commenting system. This blog uses several tactics to block comment spam but I often find myself using the spam at John Battelle's blog as a method of proactively preventing spam here.
I visit his blog, look at the recent spam he gets and copy and paste those URLs into the MT-Blacklist. It really helps but each time I do that, I feel a little guilty. The guilt comes from me benefiting in a little way from the comment spam at his blog. Just needed to get that off my chest.