If you’re trying to do marketing on Twitter the “hard but right” way (i.e., actively engaging with and listening to followers instead of just link spamming), one of the most pain-in-the-but burdens you take on is deciding who is worth following back. There was a time early in Twitter’s history when I used to auto-follow back, but as Twitter has gained in popularity and thus become a prime spambot target, I now make all follow decisions “by hand” as it were.
If you’re getting dozens (or hundreds!) of follow requests a day, that becomes a burdensome–or perhaps near impossible–task. Enter TrueTwit (http://truetwit.com/truetwit/signUp/index). TrueTwit has created what amounts to a Captcha for Twitter. Once you’ve registered your Twitter account with TrueTwit (using Twitter’s secure OAuth authorization), TrueTwit sends anyone who follows you an email asking them to reply to validate that they are a real person. You then receive email notifications from TrueTwit only for those followers who have completed the validation process. (After registering with TrueTwit, you should turn off the “email me when someone follows me” option in Twitter’s notification settings.)
You’ll still have to evaluate new followers on a case-by-case basis to see if they are worth following, but like a good front-office receptionist, TrueTwit gets rid of the riff-raff to make that task much more manageable.