NEW YORK (CNNMoney) -- SecondMarket rose to fame by offering investors a way to trade shares of the hot private companies they clamored for. Now many of those startups -- including the private market's Goliath, Facebook -- have gone public or will soon.
Facebook's IPO filing this month followed a 2011 jammed with splashy public debuts: Groupon (GRPN), LinkedIn (LNKD), Zynga (ZNGA) and Pandora (P). So where does that leave private exchanges like SecondMarket?
Dan Primack, a senior editor at Fortune, dove straight into the issue during a panel discussion on Wednesday at SecondMarket's Capitalyze East conference.
"A few months ago, you said Facebook trades made up the most volume on SecondMarket," Primack, the panel's moderator, asked SecondMarket's head of private trading. "So what does it mean, from your perspective, the day that Facebook starts trading?"
SecondMarket's Adam Oliveri confirmed that Facebook still makes up the majority of trades on his platform, "and the secondary market in general."
"Marketplaces always need something to get them going," he said. "Facebook was definitely the catalytic event. But that doesn't mean a platform goes away. EBay still exists, even though Beanie Babies went away."
Panelist Adam Dinow, a venture capital lawyer at Wilson Sonsini Goodrich and Rosati, agreed that Facebook has a halo effect on the market in general.
"Facebook legitimized [secondary trading]," Dinow said. "There were a lot of companies that didn't understand it. This brought it to the masses, which means SecondMarket will still have a purpose even after big companies go public."
Which begs the question: For which companies? Can anything replace the buzz of Facebook?
"Can we legitimately think that in a few years, the secondary market will be vibrant for life sciences, enterprise hardware, health care...?" Primack asked the panel.
It's an open and critical question, but that line of discussion veered into a chat about where the tech market's white-hot center is at the moment.
"If you go back to the '90s, it was about PCs and then it was dot-coms," said Duncan Davidson, founder of venture fund Bullpen Capital. "This area is about social, because it's the cluster that's showing very fast valuation pops."
"Well, there's another word for valuation pop: bubble," Primack said, prompting laughter from the audience.
"Dot-com fell to earth, but you lay the railroad tracks for the future on top of that," Davidson replied. "A bubble isn't bad as far as innovation, and people forget that."
"Yeah, but it's bad for investors," Primack shot back.
Lou Kerner, a social media analyst formerly at Wedbush Securities, brought up a theme that's common in his notes to clients: social media as "the second Internet."
"That siloed Internet we had in the '90s is happening again with social," said Kerner, who now runs the Second Internet Fund.
And then he made an unlikely comparison: "Facebook is the new AOL."
"No, really," Kerner protested after audience members laughed. "[Facebook] is creating this whole ecosystem where others can grow with and around it. Of course, let's hope Facebook will fare better in the long term." 
