My biggest issue is that I've worked hard to keep people visiting my site, and hopefully even clicking on ads now and then. I've done a pretty good job of cultivating an audience that delivers a lot of impressions considering the relatively small potential audience overall. I don't want people to have a reason to go elsewhere. (For the record, I also have alternate means of revenue, including premium/subscription content.)
Of course this all comes to the age-old debate about who owns the bits after they come down the wire. I'm not naive enough to think that I should have full control of that content when it lands on the client, but I'm not going to side with the inevitable response from Google that will go something like, "It's good for our customers." (Where have we heard that before?)
It will be interesting to see how this pans out in the court of public opinion.