Check out this update from the Google Content team. In a nutshell, Google is now serving ads to Gmail users based on either the current email they are reading, or based on another message in the Inbox, even if it isn’t currently being read. The reason is that sometimes Google ‘can’t find a relevant ad’ for the current email message. But, as Google’s own example shows, another reason is that it is a lot more profitable for Google to run travel ads than it is “happy birthday card” ads.
As with AdWords, Google is increasingly coming up with ways to reduce the number of auctions at any given time, thereby increasing competition (and bid prices) on fewer and fewer keywords. The same is happening now on GCN, where semantic relevance has now become “broad match semantic relevance” basically on Gmail. Inevitably, this will push out low CPC topics and reward higher ones.
I don’t have a problem with this, except that I’d rather Google stop pretending this is all for the good of the mighty user, and not their bottom line.