They're releasing the source. From the third paragraph of the second page:

"Other Web browsers could also employ Instant Pages, because Google has released the necessary code for all to use. "We are opening up the code because we want other browsers to implement it—it is good for the users and for the Web," said Singhal."

Even if this weren't the case, as drivebyacct2 said, this doesn't do anything to make us dependent on them, especially when compared to gmail or google docs.

They're offering a feature that people will like but nothing prevents me from going elsewhere. I don't see how this increases my dependence on them. Relying on them to control all of my email access, storage, etc? Yes, that makes me dependent on them. Pages loading faster? Meh.

And besides, this is a Chrome browser feature. Google would extend Bing the same curtosey, and even if not, Bing could make an extension or do the same with IE9, etc, etc.