I don't have any scientific evidence to back up a full-fledged assertion, but I have always suspected that a key success factor behind the simple text ads that comprise search marketing is their subtleness. They look just like natural search results, and I don't think most consumers actually understand the difference. I run Google ads on my blog, and last month I received this note from Google:

Until today, I didn't fully appreciate how aggressive Google had become with its desire to own datacenters around the world. Of course I have heard countless stories of the massive server farms Google operates. One rumor even suggested Google built a meaningful single digit percentage of all PCs last year. Still, I was stunned to learn from a young New York based startup about its recent run-in

Some people have such great phone voices that it's hard not to want to talk to them. A multi-hundred million industry emerged based on that observation. Marketers persuaded consumers to call 1-900 lines (often, though not always, for sex chat) and relied on their operators' ability to give good phone to keep consumers engaged as the bills ran up at the tune of $5 per minute. Excellent reporters