Governments ? do u mean this ?? there is nothing about that dude .... governments is blocking Google search results but they have no special method to block ads, not if they contact google and say do and don't ....
If you bring up a site on a US gov't PC, most ads won't show. If you happen to see an ad and click on it, they filter it out, based on the URL identified as an ad, and it shows a "page blocked" page.