When dropping a deuce, taking a dump, dropping the kids off at the pool, etc...the fecal deposit after flushing leaves an artistic swirl of streaks and smudges behind in the bowl resembling sections of marble.
"That was a heck of a dinner, Marge! I'm sure I'll be marbling the crapper tomorrow!"
The Anti-Marking Association, or AMA, was formed at the Fable Game Board on GameFAQs. They are against the marking of any posters, except under the most extreme conditions. Still around, mostly just for fun however, though we still dont mark people.
The AMA is open to anyone willing to have fun and not mark other posters.