I find this really annoying, I use '/' to use the browser find-in-page, and apps hijacking it for their search field instead ruins it.

Yes, there are other bindings, but / is in finger-memory at this point.

I wonder if there's some sort of noscript-alike that would give you fine-grained enough control to permit exactly which keys could be intercepted by an app.

As burke noted above (http://news.ycombinator.com/item?id=4534670), pressing 's' will activate the search bar.

This was also the one thing I was missing from the post. I did try '/' as well.

It looks like ctrl-/ works.

What about Opera users?