Mollom’s been doing a simply outstanding job of blocking spam lately, after the warm-up period. Unfortunately, it appears to be doing a bang-up job of blocking legitimate, breathing humans who are trying (and failing) to comment.
I just got this spam on my blog - it got through Akismet, as so many spams do lately, but it’s worth posting (at least in image form so the spammer doesn’t get any juice from it):

My blog has been receiving spam in what looks to be a new wave of spam attacks. First, the spammers seed the whitelist by posting apparently innocuous comments with no URLs, or with a URL that doesn’t contain spam. Then, once they’re in, they wait a bit and then throw the switch. The spam starts a’comin’ and it sneaks through Spam Karma 2. Very annoying.