I have noticed the same thing about Google. My listings on Amazon come up but my B&N ones are nowhere to be found. It's just like searching on bn.com versus amazon.com with keywords/tags, etc. Such a huge difference! B&N really needs to pick things up.
My sales have also been better at Amazon, about 5 to 1 over B&N. Why? It's just a guess, but I think it's because readers can find my books a lot easier through Amazon. I know they are working on it, but how long will it take for the kinks to get worked out?
Oddly enough - I sell twice as many books on B&N as on Amazon.
I don't understand it either - because my book has been on Amazon since August, while it has been on B&N since January.
My guess is the two sites have different demographics - so the books sell at different rates.
My Amazon sales are at 586 so far this month and my B&N are at 137 total so far this month, its a little sad.
Zombie Fallout 2 : A Plague Upon your Family
Zombie Fallout 3: Coming soon!!