Updated from 1:42 p.m. ET

Investors growing increasingly nervous about the high multiples of the market's "must-own" stocks have turned their attention to the data-storage sector.

Brocade Communications

(BRCD)

, which makes fiber channel switches for storage networks, on Thursday fell $25, or 10%, to $216.

Network Appliance

(NTAP) - Get Report

, a maker of network-attached storage, or NAS, systems, dropped $5.44, or 4.5%, to $116.81, after being off 13% at one point. It has fallen nearly 30% since hitting an all-time high last week.

NetApp's decline could be linked to anxiety over the upcoming launch of a NAS product by its much larger competitor,

EMC

(EMC)

. The product is expected to be released in early November.

"This EMC thing is imminent," said

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Chase H&Q

analyst Bill Lewis. "We've telling people to be cautious ahead of the launch because of the impact it could have on NetApp's stock." (Chase H&Q hasn't done recent underwriting for either company.)

A NetApp spokesman attributed the decline to "normal sector volatility."

But the problem is probably broader than that. News of

MCI Worldcom's

(WCOM)

plans to cut its capital spending is raising fears that the sacks of dollars large corporations have earmarked for technology infrastructure are not, as many have come close to claiming, bottomless.

Accordingly, the market's hottest infrastructure plays are falling. EMC was also under pressure, off $4, or 4.4%, to $86.

Sun Microsystems

(SUNW) - Get Report

, the server-systems maker that has recently honed its focus on the booming storage industry, fell $6.63, or 6.1%, to $102.

"Aggressive growth funds, closet indexers, and tech funds have been focused on an ever shrinking universe of 'stocks that work,'" said Bill Meehan, market analyst at

Cantor Fitzgerald

. "One can only ask who's next."