A cool feature of amazon is that if you have a book coming out, & you don't direct people to them, then if they don't get a certain number of pre-orders, they won't honour any orders that have already been placed thru them & your book goes straight to backorder. Very cool.
This is why you see so many authors sending folks to pre-order for amazon. It's not because we support them, it's because we basically have to if we want them to stock our books at all, & not cancel pre-orders from people who tried to support us.
There's more that I don't fully understand about amazon reviews having some weight in the industry that makes publishers feel the need to co-operate with them also because their success depends on it.. It honestly sucks.