I have never believed it to be true that Google used data retrieved from the Google Toolbar to find new pages. However, a post by fantomaster at SEW forums, says that Google does do this. Fantomaster knows his stuff, now is he said Google found new sites with AdSense, I would not believe that.
Here is the quote in the post that addresses this specifically. Note that "enhanced" mode must be on.
Another good trick is installing the Google toolbar in spy, er, "enhanced" mode (i. e. activate PageRank) and surfing your SDs: this will send information to the Google servers and they'll send a spider along to check it out. While technically this approach doesn't give you any incoming links, we've seen pages getting ranked that way nevertheless. Don't hold your breath, though: getting good linkage is always a smart move so don't rely solely on this technique in lieu of it!