One of the largest data set for IPs is wikipedia, since it allows its editors to choose whether or not sign in when they edit. By examining an article's history, you can see the names of editors who signed-in and the IPs of those who didn't.
Take the article Gullane Entertainment Ltd. (which redirects to Gullane Entertainment, a television production company that produces children's programming, best known for the series Thomas the Tank Engine
Now, if you click on the "history" tab above the article, you can see its editing history, where you'll see that on Jan. 2, 2004, 66.185.84.204 made a small edit to the article, replacing an internal link with an external. Only a few days earlier, however, the article was created by 66.185.84.208 and had provided all of the information in it, and within a few months 66.185.84.208 edited the article again.
Now, it is fairly clear that these two IPs are the same editor, and what this illustrates is something that several commentators in other blogs have noted. No one seems to hold these IPs long.
