Everyone with a few hundred thousand to a few 10's of million shares does it when the stock moves on its own, some people do it with several hundred million and cock block the ask while sitting on the bid when the stock languishes at it's 52 week low. Some of them do this at everyone else's expense while telling folks what a great bargain they are getting while hitting the ask.

The game is to clog the ask with shares so no one else can sell unless they sell into the bid where they wait to buy cheap shares. If someone does hit the ask they are thrilled because they are selling higher and buying back off the bid lower.

This of course is called, "the Blue EXCHANGE"....