On Wednesday, SINA ( SINA ) will release its quarterly report, and investors have grown increasingly nervous about the Chinese Internet company's stock recently. Even as SINA successfully made an initial public offering of its popular microblogging site Weibo ( WB 0.26% ), investors fear that the combination of strong competition from Baidu ( BIDU -0.93% ) and a host of other players in the industry as well as the Chinese government's heightened scrutiny of Internet companies could hold back SINA from making the most of the huge growth opportunity in China.