An acquaintance from the NYTM mailing list, Elaine Lee, turned me on to the most useful, most effective anti-spam anti-autofollow bot tool I've ever seen to hit Twitter: TrueTwit.
This service detects new followers and sends them a DM on your behalf (yes, I generally despise auto DMs, but only when they're disingenuous/spammy) asking them to verify their human-ness via reCAPTCHA on the TrueTwit website.
Once the new follower has successfully solved the reCAPTCHA challenge, TrueTwit will email you a notification very similar to the basic Twitter new follower notification. (Which TrueTwit recommends you turn off -- the point IS to avoid noise, after all.) From there you can choose to view the user's profile, or ignore, as you wish.
TrueTwit reduces the amount of time you spend looking at profiles to determine whether or not someone is worth following by eliminating all the non-human accounts BAM! right off the bat. Two thumbs up! My aggravation and distraction levels just dipped a point or two.
