Peaks and valleys on the Dow

Major online companies suffered when the Dow tumbled below 10,000 yesterday — for the first time in four years.

Most notably, Google fell 4.6 percent ($17.84), hitting $369.07 before trading ended Monday. Last week AmTech's Rob Sanderson lowered his Google estimates, per appreciation of the US dollar and "concerns of the spread of economic slow-down into continental Europe."

Yahoo — which serves about 20 percent of US searches to Google's 63 percent, fell 6.2 percent ($0.99) to $15.01.

Movie streaming and rental company Netflix fell 11.4 percent ($3.31) to $25.66, following the company's more conservative revisions of guidance for Q4 sales and total subscriber numbers.

After laying off 10 percent of its workforce and making two new acquisitions, eBay fell 8.6 percent ($1.63) to 17.31.

Questioning the timing of eBay's purchases, Scott Kessler of Standard & Poor's Equity Research lowered his rating of the stock from "Strong Buy" to "Buy." "We think these deals make strategic sense over the long term, but we question the timing, valuations and consideration," he said.

Web ad sales are also expected to take big hits if consumer spending is further affected by the economic downturn. eMarketer, for example, cut its web ad spend forecast twice so far, the Associated Press observed.