Amazon? Nope, don't see them stepping up to defend the Open Web.
Facebook? Hell no.
LinkedIn? No.
Sun? Maybe if they hadn't been acquired by Oracle.
IBM? Maybe not totally ridiculous, but history doesn't paint the best picture of IBM in this regard. And they also don't really offer services over the web, like a search engine. Maybe they could scale Watson up to webscale and make that the new Google?
Wolfram? No.
DuckDuckGo? Right spirit, but I don't think they are influential enough.
Opera? Not influential enough.
Canonical? No.
Novell? Eh, no.
HP? No.
This isn't looking too promising.... :-(
Edit: Duh, I missed a big one! The Wikimedia Foundation! They are probably one of the strongest backers of the Open Web, and definitely have a little bit of influence, thanks to WIkipedia and related projects.