My previous small business would receive cold calls from people claiming to be "with Google" or "working with Google" to sell me SEO services weekly. I can see how non-technical business owners who don't understand how "the internets" work could see that as a direct association, and blaming Google themselves when they dont receive what was advertised or if the relationship goes sour.

I haven't checked, but it might be beneficial for Google to come out and say that they will never work with businesses directly to increase their online exposure outside of allowing the business to buy ad space through their official self-serve Adwords platform.

Then again, Google do have certified Adwords professionals and partner companies whose name they don't want to sully with some widely misunderstood statement, and even some of the least reputable search engine agencies offering ad-buying as a service probably have a net benefit on Google's bottom line