These raffles probably are bit grey area like
@colinsunderland stated, also and especially when you have to sign in and deposit to participate, wouldn't these also need to have permission from some authorities?
It probably wouldn't be ok if i start to to promote and sell my virtual raffle tickets all over internet. Who is paying taxes from these prizes? Who is actually arranging them (and under which license number)? How cool it is that casinos are actively taking part in arrangements (checking winners, contacting them behalf of affiliate to ask consent to provide contact details that winner can be contacted)? And few more similar points which come to head in one minute.
Running illegal lotteries without any license, any taxes etc... for sure is not cool from a regulations point of view. Would be pretty similar from that perspective if i would add some self-made slot to my site and you can make one euro spins and win prizes, top of "normal" winnings, monthly raffle between all participated players.