When we do focus groups or usability tests with small businesses, they always look at the BBB ratings of the credit card processors on our site. However, I think with our new product Samurai (for online payments - http://samurai.feefighters.com) we'll have a more savvy crowd who doesn't care too much about the BBB.
For those of you who aren't too familiar with FeeFighters - our original product is comparison shopping for credit card processing. A good chunk of our customers are e-commerce businesses, startups, and other "sophisticated" merchants, but we also have a bunch of mom and pop shops (of every sort) who care about stuff like the BBB.
As it turns out, in the couple of months since we had to take the BBB logo off, we have seen no difference whatsoever in our conversion stats.