Limiting Access for Affiliates?

Right now, I have the affiliate block setup and when affiliate's login, the block becomes visible and they have access to sales, banners, text ads, etc to use. Problem is, they also have access to all products and categories and I'm noticing people are browsing around ad not staying focused on getting banners and posting ads.

Is it setup an affiliate account that only gives a user permission to the affiliate features?

Doesn't that defeat the purpose of a product-based affiliate programme? How would affiliates know what to promote?

You could edit various templates to add an “if authenticated user is affiliate display nothing” statement, but I can't see the point, especially because they could log-out and view the site anyway unless your store is already set up to be viewed by authenticated users only.