Ok, so you provide convenience. This only works for people who don't already have an affiliate link though. If I am BigTimeBlogger and I want to share things that could earn me some money, it would probably make sense for me to create an affiliate account for the products I recommend, just so I can earn more (you take a cut of the commissions, right?). On the flip side, if I'm JoeNobody sharing a link to the camera I bought, it's very unlikely that I will create any sales with my 25 twitter followers.
If the market of people who are bigger than JoeNobody but smaller than BigTimeBlogger is big enough, then this is a service that will likely fill the market and do very well.