Try googling "GOOG" (the stock ticker symbol of Google) and you are likely to see the following ads:
Filthy rich? We'll help - Throw away your newfound cash at Woot. You're welcome.
LuxurySiliconValley.com - $3 Million+ homes and condos for sale in the Silicon Valley
Surprisingly, Google currently has no ads for people googling for BRK.B (Berkshire Hathaway Inc.) - this stock trades at 7x the stock price of Google
For MSFT (Microsoft) and YHOO (Yahoo) - the ads are related to jobs in both cases:
Write beautiful code? - www.ooyala.com/careers [Thanks Rakesh]