Google Japan did something with balloons:

http://googlejapan.blogspot.com/2008/10/blog-post.html
http://www.google.co.jp/intl/ja/landing/searchtips/
http://dekirufly.blogspot.com/
http://www.wktokyo.jp/blog/?p=904
http://www.youtube.com/watch?v=6tVlv4-8YHw

I asked someone who I figured speaks Japanese, here's their (anonymous) reply:

<<My Japanese sucks, so I wasn't able to fully understand Google's landing page. So take everything I say with a grain of salt.

Basically, there are thousands of balloons attached to a flight harness at a Google event booth in Shibuya. People can line up to strap themselves to the balloons and fly up into the sky.

Google is encouraging people to do "searches of the day" on their mobile phones using Google Mobile Search. People can go to the event staff in Shibuya and show them their mobile search results page. For every results page shown, more balloons will be inflated, so the higher people will fly. (I think). As you can tell from the pictures, there are many balloons, they are very visible and they are Googley colored!>>