In fact, there are many super internet marketers who market only affiliate products. Nothing wrong with it and highly recommended.

I do have a proviso though, and that is not to promote affiliate products without branding yourself and building your own email list of subscribers. One way of doing this is to promote your affiliate product by sending visitors to your own squeeze page first to capture their contact particulars for your own mailing list. This way, not only do you have the opportunity to continue pre-selling the affiliate product to your prospect, but you have your own prospect that you can build a relationship with all your future promotions.