The problem is that I had success with it right away and started making good money. That doesn't sound like a problem, but it is. It is a problem because
1. It wasn't a long term business model
2. It made me lazy..
I didn't have to do anything much, the checks kept coming in. It made me totally lazy. I held off creating products and looking for other ways to bring revenue. They looked so hard and took so much time compared to Adsense. I look back and think how much better base I would have now if I had not found Adsense, or at least, didn't let it take over.
Eventually Adsense turned into a turkey. Then Google killed my account for an unknown reason. Talk about building a house on sand.
FYI: The WSO section could be your drug. I see many who do nothing but create WSO's. I'm not sure that is healthy.