Earlier quoted context omitted.
in the meantime, I enabled zoom for mobile devices. Whoever turned it off in the first place was a bad person, and should feel bad for doing so.
Having zoom enabled and changing device rotation can cause formatting issues on some devices. The mobile (smartphone) websites of TechCrunch, Yahoo, Cnet, Mashable, etc. all disable mobile zoom. Tablets appear to be a different story though, and zoom might need to be enabled there.
Then fix your goddamn site instead of gimping the user's web browser.