Also such deposit bonuses are not applicable for gambling only. There are many forex trading websites offer such bonuses. Where you get $50 in bonus but the minimum to withdraw is $100. Otherwise it will become an endless circle of deposits and withdrawals, ain't it??
I had that bonus done many times, the EU actually spoiled the party so I was lucky to take part in many company offers years back. It works fine as you just play through with the cash at least once. Where it gets hard is when in either betting or anywhere if you have play through the bonus cash 10 times or more then obviously you may never get to withdraw if you lose.
Its understandable either way but I've got the offer to place a bet bonus for just taking part at least once and obviously thats the easiest and biggest draw for people who might not otherwise consider a gamble. I call it a no brainer to have a go then and I usually try to get people to take part, not everyone can recognise a good offer always but its fairly straight forward hopefully