Yep, like most of us, bookies want to maximize their profits. They do this by tweaking the odds so that an equal number of people bet on each team. Small time bookies don't have much control of the odds. When their books are out of balance they have to "lay off" bets to bigger bookies. Sorta like buying loss prevention insurance. There is a science to this...The bookies set lines that will produce an equal amount of wagering on either team. Lines get adjusted or not based on the betting. If you hear of a bookie who "got killed" on a certain game then it's likely that it wasn't a bookie but a gambler who sat on some wagers. That isn't bookmaking.