Tritto
A word created by Topaz Mutiny. A portmanteau of the words ditto and tri (or three) it has become a replacement word for a person dittoing something someone has already 'dittoed', or 'as welled', or any other such agreement. Its subsequent 'dittos' include quadritto, quintitto, sectitto, septitto, and so forth. It gained popularity enough in the AIM/AOL chatrooms to be notable.
So far, the longest chain of trittos has been sectitto, or 5 dittos plus the original statement.