XO Communications

Location: Herndon, Va.

Why it's so cutting-edge: XO is another company that has been very aggressive in the ultra-competitive Ethernet market. It recently took steps toward better management of its external network-to-network Ethernet interfaces, greatly expanded Ethernet availability earlier this year, and extended its reach for Ethernet over copper. Not to be outdone by wireless carriers, the company developed its Anywhere initiative with mobile workers in mind. XO was another Honorable Mention on last year's list.

But can it keep its edge? Some investors were unhappy earlier this year with XO Holdings chairman and busy billionaire Carl Icahn. XO had a decent second quarter, but it's one of the companies that will be watched closely for sign of possible declines in enterprise spending to come.

XO Communications
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