Google, whose stock was worth $741 a share a year ago - and was touted as inevitably seeing $1,000 - hasn't been able to hold its head above $300 because of widespread fears of advertising collapsing.

The stock slipped to a multi-year low today below $290, down ~7% in the midst of another 350 point drop in the Dow Jones. Google hasn't been below $300 since October of 2005.

That gives the mighty company a market cap of only ~$90.65 billion, half of Microsoft's. Microsoft has also been roughed up but not as dramatically as Google.

Today's retreat was set off by still more analysts cutting their estimates on the company's Q4 results. On average they figure it should clear $5.12 a share on $4.3 billion in net revenue.

Meanwhile, Google competitor Yahoo, which snubbed Microsoft's $31 a share opening bid, is scrapping 10 bucks, down another ~11%.