I haven't noticed it as when I buy books from any bookseller I already know I want.
I will say that as a local to Powell's, I love the fact that they've partnered with google books. In fact, it was that partnership that made me go with a Sony eBook reader in the first place.
Perhaps you can contact their tech department and let them know? The two times I've interacted with their help department has resulted in site stability and good things.
/innowen