Hmm, never heard of Bouncer before--will have to check that out!
I think that Amazon actually manually tests all new apps to make sure they work as advertised / submitted (or at least they used to).
I've submitted a few apps to the Amazon app store and early on, it was quite a while before they were approved and I don't believe that it was because they were overwhelmed--I actually think they were testing out the various parts of the apps (in one case, I had a copyrighted image they pointed-out to me that I needed to update/replace before they would approve (it was a Batman logo, in case you were wondering
). This actually impressed me quite a bit
So, I don't know for sure the details, but here's a story from when they started about them vetting things: Amazon Is Vetting Android Apps for a New Online Store | NewsFactor Network
Oh, I forgot, in the developer console and for when an app is submitted, there's actually a section where they ask for details about how to test the app being submitted.
I can only surmise that they also subject new submissions to some kind of virus scanner, too--would not surprise me in the least and I would actually be surprised if they didn't.
Cheers and I hope that helps!