Hehe, that sure is some juicy promotions! I don't get why some casinos will risk their "hard earned" reputation by conjuring up these silly moneytraps.
I had a look see at other "bonus offers" colosseum is making. This is from their new customer sign up:
Code:
To WITHDRAW your original deposit and bonus you need to fulfill the following two requirements:
1. YOU MUST WITHDRAW at least the original amount deposited plus double the bonus - Please note that you cannot double the bonus by playing the following games: Roulette, Baccarat, Craps, Blackjack, Red Dog, Sic Bo, Video Poker, Table Poker and all variations of these games.
Exp.$/£€ 100 deposit PLUS 2 x 100 PLUS 2 x $/£/€15 PLUS 2 x $/£/€20 Neteller/Firepay = $/£/€370 in your account.
2. YOU MUST WAGER an amount equal to the deposit PLUS 5 times the amount of the Bonus – Please note that you cannot wager the bonus by playing the following games: Roulette, Baccarat, Craps, Blackjack, Red Dog, Sic Bo, Video Poker, Table Poker and all variations of these games.
Exp.$/£/€ 100 deposited PLUS 5 x $/£/€ 100 bonus PLUS 5 x 15 Sign in Bonus PLUS 5 x 20 Neteller/Firepay = $/£/€ 775 wagered.
In other words you're
only allowed to play slots. And if you do you will bust out 99% of the times trying to double your money!
We hope you had as much fun as we did con'ing your money from you 
I mean come on. Why not just cancel these kinds of "promotions" - the only thing you're "promoting" is your lust for more money.
If you're so scared of bonus-hunters - don't do moronic sign-up bonuses. Do some wicked comp program instead!