Complex sentence: The main concerns have been quality of accounts and quality of user data provided by Qihoo 360, the short sellers have mainly pointed to the discrepancy in reporting figures market shares between Qihoo 360 and firms such as Baidu.
Split into simpler sentences: The main concerns have been quality of accounts and quality of user data provided by Qihoo 360. The short sellers have mainly pointed to the discrepancy in reporting figures market shares between Qihoo 360 and firms such as Baidu.