Yes. But there are two options...you can be a normal BBB member, or a BBB Online member. They're different. To get the seal on your site legally, you have to pay for the normal BBB membership and then an additional fee for the online part.
I'm in my second year. Can't really say it's brought in any sales (though I can monitor clicks on it) but it's almost like an insurance policy for my potential and current customers that they know they have somewhere to go to report me if I wasn't providing what I guarantee.
That's the reason I keep it and look for similiar businesses to interact with.
So I don't think it will be a big sales driver, but it won't hurt if your budget can spare it.