360.cn was developed by Qihoo, a Beijing-based community search company. There has been some controversy surrounding Qihoo and its 360 security suite, such as it reporting other anti-virus software and search tools as being malicious (reference) and doing QQ (IM/chat) session hijacking (reference). Within the past year of Qihoo going public, there have been further controversies - including reports of the company spying, hacking, and leaking data (reference). And then there are the rumors that the 360 software includes spyware - and that they may have affiliations with PRC Gov't to track, monitor, and police user's online activity (reference).

As Mike points out, this is a tough and controversial question. An interesting read, and likely to provoke a lively discussion!