A constant annoyance with managing website today is the level of spam that comes in through comments, forum posts, contact requests, user registrations, etc, etc, etc... Not only can spam messages make your site look like crap, if you have any sort of comment reply notification (as this site has) you can end up emailing spam to your visitors, which will turn off a LOT of people. There are times when you don't seem to be getting much and then other times when it seems your site is being flooded with this junk - this week feels like the latter.
There are several ways of dealing with spam: