Karl von Laudermann
Hitting "Enter" after you type in your search words will start the search.
I realise that this is related to tablets, but as I don't have one, maybe they don't work that way, but that just seems stupid to me.
On iOS, a Go button appears on the keyboard itself, so you are correct that the user could use that instead of the one in the page. I don't know about Android or other tablets, however.