We are hearing reports from several publishers in the Google AdSense network that Google is testing larger font types in their ads.
Some like the larger fonts because they feel it draws more attention to the ads, which leads to more clicks and more earnings. But some don't like how the large fonts stand out. They feel it distracts from the content on the site and they have no way to downsize the font.
Maybe this will lead to giving publishers control over the font size, like they recently did with AdSense Font Types just last week.
JenSense has some pictures of the larger font types being tested.