The main reason that online casinos give you cash to play at there casino, is in hopes that you will enjoy the experience and become a loyal player. This is a loss the casino is will to take a chance on since they have confidence you will like the online casino. You have to remember this changes all payout odds for all players when free cash is given as everything in the casino is based on payout percentages and more play means games will payout. So the online casinos do not take kindly to players trying to cheat the casinos and abuse the promotion. This includes signing up more than one person within a household to just take the free money. The online casinos do keep track of players computer id's, your internet ip and other common factors. So don't think they will not know, they will and you will be put on a blacklist. Just play fair, if you expect the casinos to.