In a similar move to the one they used on Hachette Books, Amazon has removed the option for preorders for some Warner Bros DVDs while they are negotiating the terms of a contract. 

The Wire tried to preorder two movies which come out June 17th, and found the 'Pre-order' button is mysteriously missing on the Warner Bros selection, "The Lego Movie":

Here's how it looks for a non-Warners Bros movie available the same day:

For books, preorders help determine best seller lists, where as already released movies are a bit different, it's just the matter of profits. 

As with Hachette, the Warner Bros move is just a flexing of Amazon's negotiation muscles. Amazon is completely in their right to do this, but has stayed distinctly more quiet on this front. They have not replied to The Wire's request for comment, nor to CNN Money or The New York Times. They were quite clear with Hachette, that book buyers are free to go elsewhere.

Perhaps Amazon is staking their claim on this powerful negotiation tactic, or perhaps they have been doing this for years, and consumers are just now more alert.

Still, as with Hachette preorders, once that Lego Movie hits the e-shelves for $0.99 less than the competitor, you might find yourself more loyal to your wallet than an online retailer that doesn't have harsh negotiation tactics.