"I can attest to having been extremely frustrated doing web searches trying to find things like software, templates, standard documents, and legal agreements to help me grow my business.
But when advertisers of such services start to put their little classified ads up next to those keywords, the process gets a lot faster. I still use PDF Factory Pro, for example, because I saw their ad on Google next to a jumble of useless results for my web searches on PDF publishing."
Hear, hear! I find myself actively looking for the ads when I’m doing product/shopping-related queries, as sometimes all I want is to know where to buy the freaking stuff and how much it costs. Someone explaining why they offered the thing for their grandma for Christmas, or an obscure academic paper which happens to include my query’s keywords, is sometimes just noise. It’s all about context.
01/14/05 update: Google search within sponsored links.
05/30/05 update: indirectly related: Yahoo Mindset.