Two recent discoveries:

1) Twitter lists are really handy if you have someone who is copying tweets. Just make a list which has both them and the people they are copying. Anyone who reads the list can see who posted it first.

For example, I heard that that @britishchris84) was copying @ComedyTeddy so I made a list:

http://twitter.com/tweetthief/britishchris84

2) If you “favorite” a tweet by someone who later changes their account to “private” you can still see if they have deleted the tweet or not. So I make sure to “Favorite” any tweet which is stolen (and also the original) which makes it easy to go back later and see if they have deleted it (if you only see one, then it’s the original). NOTE: If someone does delete the copied version, I “unfavorite” the original, because I no longer need to track it.

So I went through the list that I made and marked off all the copied ones, and now I can check

http://twitter.com/tweetthief/favorites and see if/when @britishchris84 deletes the stolen tweets.