Maybe, there seems to be an number of grey areas.
Google Adsense, believe it or not is used by a huge portion of
Application Developers on Facebook for many reasons, even though
technically Google Adsense, isn’t designed for Social Sites like
Facebook, and thus won’t always approve. Applications on Facebook is a
complex juggle to manage to make profitable, using Adverts is just one
of them. “Virtual Currency” is a popular choice to go in addition, but
that's a topic for another Article.
You run the risk of having the account suspended potentially, since
Google Adsense TOS does not permit the use of IFrames to display
their ads. so you take my advice at your own risk. Don’t over do it
with Ads on your Canvas page, I recommend one, at most 2 per page, and
the pages which you put the ads on within the frames, ensure their is
a lot of content, and not just keywords there.