Facebook eyes mobile firm Opera to help it launch its own smartphone Facebook and its Wall Street advisers are now being sued by investors who lost out in the $16bn initial public offering, amid claims they were misled about its business prospects. Shares, which placed at $38, were trading at just above $30 in morning trading in New York. Just before the botched IPO, the social network issued what was effectively a profit warning because it has not yet worked out how to monetise mobile usage sufficiently. The social network told investors that the number of users accessing Facebook on their mobiles and tablets was growing much faster than its mobile revenues because it has not yet cracked how to advertise on smartphone handsets. The warning followed an earlier admission in Facebook's IPO filings that the rug could be pulled from underneath the business if one of the established mobile giants decided to block Facebook's services. We are dependent on the inter-operability of Facebook with popular mobile operating systems that we do not control. [Any changes that] give preferential treatment to competitive products could adversely affect Facebook," it said in its S-1 filing to the Securities and Exchange Commission. Google could use its "strong or dominant positions" in different markets to make "access to Facebook more difficult," it said. The social network is now trying to take control, said analysts. "Opera would enhance the now limited mobile experience of Facebook, improve Facebook's mobile monetization problem, help Facebook retain online game developers leaving the social network over a lacking mobile platform and further improve Facebook's ability to target ads," said analysts at Arctic Securities. Separately, Edouardo Saverin, the former Harvard student whose court case against Mr Zuckerber was dramatised in the film, The Social Network, has said he has "no hard feelings" over the row which ousted him from the firm. He said he has "only good things to say about Mark" and praised his "visionary" focus. Mr Saverin, whose shares in Facebook are now worth $1.75bn, also defended his move to Singapore, saying it was for work reasons rather than to avoid paying tax on his windfall.