User blog comment:NeneAndNate/Rollback/@comment-2093602-20110219153833

Rollback allows you to quickly and easily revert the last edits. This can be used for vandalism/spamming etc. Unlike with Undo, you don't get the edit screen and the text doesn't need to be "saved" before it to take effect (if you press Rollback, the edit is instantly undone).

It only works with the last edit of the page though (or more if the last edits are all by the same person).