When you register a domain name, you have 5 days to give it back for a full refund. This paved the way for "domain tasters" to monetize their efforts by placing AdSense ads on these temporary pages. Domain tasting is the act of registering a domain or many domains to get a taste of their traffic, then returning them if they don't meet a certain threshold.
At least one Google partner was making over $3 million per month by putting ads on these temporary domains. Google decided to make sure these people weren't cashing in like this by introducing a new rule -- Google won't pay out for on a domain that is less than 5 days old. This doesn't stop people from switching to another ad provider, but just by doing this, other companies may be tempted to do the same thing.
This is a smart policy move on Google’s part to ward off impending litigation that might have hit them in the coming months. Trademark lawyers have been getting crafter at taking down Kiting by suing under other laws. The new weapon of choice is not using Trademark laws but Forgery laws. The penalty for forgery is much worse and cares a much higher fine per article that is forged. Dell, Yahoo, and BMW have all filed lawsuits in the last two months that ask for millions of dollars of damage from Google partners and I think Google sees the writing on the wall, they might be named next. -- DomainTools blog
Will Yahoo turn on on Domain Tasters too though? There is a good chance they will because they are already suing domain tasters under the forgery law mentioned above. Due to this AdSense update, all those people who were taking advantage of the system will be looking for money elsewhere, and the next likely choice is Yahoo. Now Yahoo has to decide whether to play nice and cash in on same people they are suing, or kick them where it hurts. It should be interesting!