http://news.cnet.com/8301-1023_3-57590987-93/ftc-to-search-engines-make-it-clear-which-results-are-ads/
Before clicking through I was going to say, "haven't we heard this before?" That was 2002?! Time flies...
Do you know what the rules are for print? I believe the "advertorial" ads are required to use a different font among other things.
Personally, I add Google Ads to my personal stylesheet for my browser - it had gotten to the point that on most display I was unable to tell the difference