Google doesn’t like Yahoo! URLs in their Placements
Don’t try to add yahoo.com as a website targeting option in Adwords (placement targeting) or the new Google/Doubleclick exchange. If you try to add yahoo.com to a campaign you will see a screenshot similar to this.
Google will allow you to add all other 199 sites in the Quantcast top 200, including Microsoft.com, Bing.com, Facebook.com and others (even google.com). Looks like some engineers were having some fun. It seems silly to single one site out among a large variety of ones, friend and foe alike.