Lately we've been dealing with about three people who keep trying to get around the system with multiple accounts, resulting in about a dozen bans in a pretty short period. The secondary accounts prettymuch all get spotted and banned within a few days of their registration, so maybe that's what you're seeing.

Also, a possibly unusual amount of people who have been screwing around for a long time are getting into their final warning zone and then banned. They didn't start at the same time, but I guess as they spent time around one another, their cycles got synchronized. Like with the menses.