For most types of ads and products, the value of these ads is probably more in product awareness. You know that a lot of people are seeing your ad. It's in a prime location; people can't help but see it. Next time they want to gamble, maybe they'll think about your casino. It's pretty unlikely IMO that people will want to drop their current activity and start gambling right now after seeing your ad. Similarly, people aren't going to immediately go preorder a BFL unit after seeing their ads, but if they ever want to get into ASIC mining, they're likely to think of BFL first because BFL had ads here for so long.

Ads demanding immediate action rather than just promoting a product will probably get many more clicks. Like:
    CaesarBIT: Gamble with double deposit at lowest house edge
    Click this ad to get $5 free credit -- this week only

But I'm not an advertising expert. People serious about advertising here might do well to contact someone who specializes in developing effective advertising strategies.