"You really have to buy into the idea that LinkedIn's revenue is going to grow 10-fold from here to justify its valuation," Wedbush Securities analyst Michael Pachter said. "It's a good company with an expensive stock."
LinkedIn's success also could attract more competition. The company's biggest threat, of course, is Facebook, which already knows where most of its users work and where they went to school.
Weiner isn't worried about Facebook expanding into LinkedIn's turf because the company's research indicates that most people want a dividing line between their professional and personal identities.
Facebook hasn't yet shown any desire to open a professional networking channel, but Pachter thinks there is a greater likelihood of it happening if LinkedIn continues to do well.
"Facebook could just say, 'Hey are you tired of going to LinkedIn? Just enter all your professional information here and we'll code it so only your business friends can see it,'" Pachter said.
Another alternative would be for Facebook to buy LinkedIn. But Pachter doubts that will happen now that LinkedIn is worth so much.
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