Spam Control
I hate spambots. One of the reasons I went with a popular CMS like WordPress is because there are bound to be spam block tools integrated with it, or other nice people will create good blockers 
And so far, most of the blocking by WordPress and plugins has relied on IP blocks, captchas, etc. The scourge of the Texas-Holdem-Online-Poker nonsense has been contained very effectively – especially with SpamKarma and ReferrerKarma.
However, one problem that existed earlier, and has worsened are spambot-spiders. Seems a lot of the user-agent strings that crawl the websites these days are random bots. If you look at the logs, the way they behave makes you feel they are trying to get around the throttling checks, etc. And the way they land up right in the middle of the website, without following links or from a web-search makes you wonder where they got the link database from..
So, after looking around a bit, I got this nice link Stopping Spambots: A Spambot Trap. Most of the stuff there is easy to setup, so will implement. Makes sense too. No point giving bandwidth to unknown crawlers that dont follow robots.txt.