If you get a reputation for trying to sell people on stuff that just isn't very good (read, things that suck!) that is a rep you'll have a tough time shaking off.

The simple fact is, fortunately, it's one of the easiest problems to avoid.

You just need to pick good products.
A common misconception is that it's better to promote cheaper products. That more people will buy. That may be true. I mean, it's not a problem for most people to throw a couple of bucks...