There's a story out there on it from a year or so ago, it was last known to be called in the NFL or major college, in 1991. The officials are apparently instructed to only call it in extremely blatant situations where the ball carrier has absolutely no way to move the the ball forward on their own. The 1991 call featured a player laying flat on his back on top of players, being dragged by a very stretched jersey, into the endzone. One ref in the article said he didn't call it once in his 40 year career at any level of football.