A recent bug in twitter was found which literally forces any account to follow you. The flaw appears when a user tweets this format: "accept [Twitter Username]". That user then appears as one of your followers. For example "accept TheBulkTwitExp" will cause the Twitter account "TheBulkTwitExp" to follow you.

Twitter have noticed the error and have been trying to fix it. When users attempted to run the command, (or any other command at the moment) they receive the "internal server error" message. This is the reason why you are seeing people Tweet the same thing multiple times. It also seems that people cannot see any Tweets on other peoples profiles.

Twitter's attempt to squash this bug is to reset the accounts of anyone who tries this exploit to a follower count of zero. Once that's complete the follow/ing/ers counts are being set back to what they should be. Hopefully they will sort it out soon.