I had to get on the CAPTCHA bandwagon
Blog spamming was never something that a blogger can ignore, but the problem of comment spam had mostly been taken care of by Akismet which works incredibly well – lately it have let through only a few false negatives a month.
Registration spamming on the other hand is rather new – I’ve been getting a lot of these (several hits a day) only in the last half a year or so. I’m still not sure what they are trying to do – its not like registered user are exposed to less strict spam checking and even Akismet false negatives do not show up on the site: I have to approve 1st time commenters by hand, so comment spamming basically just spams the administrator.