Besides the Internet sector, software is also expected to be a high point this year, with companies like data security services company Imperva ( IMPV), service revenue management firm ServiceSource ( SREV) and telecom expense management provider Tangoe ( TNGO) ranking as the top performing tech IPOs of 2011, according to Dealogic. There's 35 tech companies in the IPO pipline, including high-profile names like Yelp, Kayak and Brightcove, as well as several in the so-called shadow back-log, meaning the company hasn't yet filed its S-1 but is expected to do so soon. Other tech companies expected to go public this year include Twitter, Gilt Groupe and daily coupon firm Living Social. As more marquee Internet firms go public, it remains unclear what 2012 will bring for markets like SecondMarket and SharesPost, which specialize in trading shares of private companies. In the last year there's been significant investor demand for companies like Facebook, Foursquare and Box.net which have chosen to remain private and take additional venture capital rather than access the public markets. "Secondary markets may augment public markets but they're not going to replace the public markets," said Tom Fox, head of global capital markets at UBS at a recent IPO briefing with reporters. --Written by Olivia Oran in New York. >To follow the writer on Twitter, go to http://twitter.com/Ozoran. >To submit a news tip, send an email to: firstname.lastname@example.org.