http://www.google.com/trends?q=bitcoinMore Bitcoins are currently made each day than bought. It takes a huge influx of new buyers for the price to shoot up as with the $30 high.
Google trends shows several things, most importantly how many people have just heard about Bitcoin and want to find out more. There will be a conversion rate between searching for Bitcoin in Google and purchasing Bitcoins at an exchange. Sadly that info is not public knowledge but it's possible the big exchanges track conversions with Google analytics.