I think it's a great idea. If you hear a catchy tune on the radio and it gets stuck in your head, and you don't know the artist, Humming Search could save your sanity. Plus, it's cool.
Or it would be if it worked. I tried humming several tunes into my computer and got only one hit ("Come As You Are," by Nirvana). My wife, a Juilliard-trained musician who swore at the machine when it couldn't pick up "Yellow Submarine," after we both hummed it ("And you were even on key!" she said), had slightly better luck--Nayio ID'd about 30 percent of the songs she hummed and sang.
Once--or rather, if--Nayio identifies a song you've hummed, it redirects you to Napster, where you can listen to the real version and buy a download.
While I think the idea is cool, my wife was unimpressed, both by the implementation and the concept. She says friends are better at identifying music than computers are: "Hum into a computer or phone a friend? I know what I'd rather do."