I'm not saying DO IT. But you only make money through Adsense for search when an ad is clicked. I don't think you make money via ecpm but with that said I don't see the big deal of going to google.com and with that said from the mouth of Google
And a valid reason for not doing that is that when you search on your site you distort the averages between searchs and clicks. So whether you intend to or not you are messing up the system. As others said don't do nothing google on your own sites.