the effect will be minimal (if any at all). there are other ways of getting the message of bitcoin to people. however, ask yourself this. would there be a positive impact on bitcoin when google start advertising bitcoin? probably a bit, but not so much in the way that we'll feel it when google removes the ads again.
Google already is advertising bitcoins.Just type in the browser "Best Bitcoin Wallets" and you should see the sponsored adds on the left.
![Grin](https://bitcointalk.org/Smileys/default/grin.gif)
Matter of fact,no ponzi's/exchange sites are being shown at the ad results but sure they're doing on the independent adsense based add engines.Doesn't really help promote bitcoin or anything but helping the businesses with the right customers.