In answer to your question, I believe all bonuses are the cause of most player issues and withdrawal disputes. They certainly cause headaches and bad press for casinos. But they continue to use them, why?
A few weeks ago I added an article over at DOCH centering around the Bogus Bonus Scam. It certainly sheds light on what some affiliate programs are doing with these comps and how they could scam affiliates.
I play exclusively at 32Red and Dash, being a VIP I don’t have an hassles. Though there are other casinos which seem to produce more than their fair share of complaints when it comes to bonus comps.