Agree with the above response. You may have a website that receives 5,000 unique visitors per month and make little or no money from your affiliate programs.
In my own experience, Commision Junction is a waste of time because you might get as many or as little leads, clicks or sales that are usually deducted from your balance when the advertiser is flagged as "deactivated." I was never able to get a single payment from them in about 5 years.
Other individual affiliate programs may work, but it's all about your niche. If you have a fan page and you add Allposters, you are probably chosing the right affiliate program to target your audience, but they will hardly buy SEO tools, just to name an example.