what's the use discussing the matter here? if anyone feels there is a violation, report it to Google: https://www.google.com/adsense/support/bin/request.py?contact=violation_report&hl=en_GB
Who said it is not allowed, You said you had simple page and he have search engine, He is promoting Google search more. So he wont be
Why does it bother you so much? You think it's not allow? Don't do it to be on the safe side. You want to try? Try it. No risk no gain . Else..... leave that guy alone
Dunno why people keep saying that , but you can not use a search form on a page with no content .Anyway he's not the only 1 i've seen around net that use to do this
Dude, Blackle.com is using adsense for search on a single page and has a PR6 and an alexa rank of 5K. Dont hate, lol.
Well only thing which I think is you might be banned on Private Policy issue on that domain! Did you mention Policy on your search page? This fellow have Private Policy on his page!