I'm a bit worried with the signature campaign. I have read in the September thread that the site spent about 12BTC that way last month (
https://bitcointalk.org/index.php?topic=758854.msg8625679#msg8625679). So, with a 0.1% edge for the casino (10% of the 1% edge), just to compensate that expense, 12 000 BTC have to be wagered per month. I wonder how much dicebitcoin expects to be wagered on the casino, but I think he's spending too much in that promotion.
They've been averaging over 1000 BTC wagered per day (19k wagered in the last 14 days) recently, so it's quite likely advertising expenses aren't going to kill them.
Also they probably feel that it's worth spending coins to get themselves established. There are a *lot* of dice sites out there with not an awful lot of differentiation between them. If advertising heavily can pull in just a single large (and unlucky!) player, it's worth it.