There are definitely many legitimate offers, and as long as you read the fine print and follow the instructions, you should not have any trouble getting whatever the affiliates promise you. I have myself completed several of them (on PSO and other sites), and the main caution I would give is that the minimum deposit is usually not going to be enough to earn enough points in the allotted time, unless you play grossly outside your BR (which usually means you'll go broke before you complete the offer). But, as long as you're aware of that and deposit enough to play the proper limits and # of
hands within the offer time frame - usually 60-90 days - earning the points requirement is usually pretty easy.
Having said that, there IS one HUGE drawback to signing up with any "free gift" or "free $$" offer (imho), and that's the fact that your account will then be forever tied to the corresponding affiliate, and you will most likely never get anything else from them after receiving your initial "reward". If you are just going to play at a certain site for that particular reward and then withdraw and move on, that might be ok, but if you plan on sticking around and playing there a lot (especially cash games), then you will be paying full rake forever, when you could have instead signed up for a rakeback deal that pays you on avg about 30% of your rake back on all your play -- in the long run, that is going to surpass the value of whatever sign-up reward you might have received 100-, if not 1000-fold.
So, in short, while I have successfully completed "free whatever" sign-up offers in the past, I am now stuck without rakeback on several sites, and there's nothing I can do about it. Fortunately, I figured this out in time to find some good sites where I still could get rakeback, and I have since signed up and moved my cash game play to those sites, but I'm still occasionally beating my head against the wall (not literally...just like this:banghead
about not doing more research before signing up for those "free" offers and "wasting" my rakeback opportunities at sites like Carbon and Cake....