Yahoo!'s Long Casualty List

Updated from 7:51 a.m. EDT

An unspectacular quarter and disappointing guidance from Yahoo!(YHOO Quote) took a heavy toll on both Internet search-engine stocks and the larger universe of speculative technology names.

Yahoo! plunged $3.62, or 11.1%, to $28.98 in premarket trading Thursday after delivering second-quarter revenue about $2 million short of estimates and saying third-quarter revenue would be $610 million to $650 million, on the weak side of the First Call consensus of $646 million.

Joining Yahoo! in the downdraft were the two stocks most closely associated with its post-bubble arc: Amazon.com(AMZN Quote) and eBay(EBAY Quote).

Amazon, which was roughly flat for the year but up 25% from its early May low at the close of trading Wednesday, skidded $2.59, or 5.1%, to $48.41 in premarket action.

eBay, which had risen 28% in the year to date, tanked $3.67, or 4.2%, to $83.20 in premarket action. Meanwhile, discount site Overstock.com(OSTK Quote) fell $1.86, or 4.8%, to $36.41 in after hours trading Wednesday.

While all three stocks felt immediate pressure on Yahoo's guidance, the Internet sector was also the subject of negative research issued earlier in the day by Prudential Securities. Prudential downgraded eBay to neutral from overweight, citing its runup and the potential for demand problems over the summer.

"As we head into the seasonally slower summer months when Internet usage and fundamental growth rates typically decelerate, we believe the sector could experience added volatility and downside risk," the brokerage said.

Several search engines saw their shares slide, including Looksmart(LOOK Quote), Mamma.com(MAMA Quote), AskJeeves(ASKJ Quote), and FindWhat(FWHT Quote).

Another casualty was the Web advertising space. Shares in Infospace(INSP Quote), DoubleClick(DCLK Quote), and tech-news site CNet(CNET Quote) all fell after the bell Wednesday.