Earlier today, we were overwhelmed with reports of follower counts dropping for many users, as a result of Twitter's purge of spammy accounts.
We still haven't noticed a (significant) change in our personal accounts or Mashable's Twitter account, but it's possible that this change is being delivered gradually and that some accounts will be affected later than others. We'll be monitoring Twitterholic closely to see how the accounts with very large number of followers have been affected; for now, we've seen some significant but not-too-dramatic drop at some of the top users such as Ellen DeGeneres.