bw100 - 2:27 pm on Jul 30, 2011 (gmt 0)
The adwords blog had something on this a while ago.
If you believe what they say and what you see, it seems an annotation indicating that you +1'd an ad would appear in the ad, the next time that ad showed to one of your "friends".
will Google ever "Inject an "Ad" into the same box that shows what my friends like.
Whether it would cause the ad to appear to your "friends", in the context of their browsing or reading unrelated subject matter, is not clear in their documents. Google probably didn't know when they wrote this. If I was going to guess, I would think it likely, for the purposes of adding value to the +1 service. Also, the display of your name as an endorsement (which is what it is) might generate clicks for them.
Regardless of whether the website has signed on to use Adsense or not
Injecting this into the website without agreement of the owner wouldn't fly too far. However, I vaguely remember reading about a patent (?) regarding displaying content in the empty space on a browser.
There are, however, other ways to accomplish the same result, just not within the website content.
I can't for the life of me understand why someone would +1 an for the subject matter (Television on sale, cruise, etc.). I might click on the ad, +1 that site's page if I liked it, more likely email the link to a friend that I knew had a timely interest in the subject matter.