What browser are you using? You see results marked as AMP when searching from desktop?

Firefox 51.0 for Windows, with the default user-agent, I get amp.google.com links scattered through my search results. Seems extra prevalent when I'm searching for news items, a lot of TV news station articles will come back with AMP URLs.

Nothing. Bing has already started using AMP in their results.

Bing has actually started using AMP in their results. See the last paragraph of this article: https://techcrunch.com/2016/09/20/google-brings-non-news-amp...

The change is still rolling out and is not yet available for all users. But if you search for something like "obama" you can see AMP already in use in the "Top Stories" section of the results page

No, there is built in support for ads in the AMPHTML framework, see: https://github.com/ampproject/amphtml/blob/master/builtins/a...