Actually I know ESL recruiters in China, both Chinese and foreigners ( as Larry from Taizhou, the infamous American recruiter) who are worse than Frank zhang. Lots of false prophets call themselves recruiters ready to sell you as a piece of meat on the luring ESL market in China, making false promises and treating you like shit.
Personally I think most of the ESL agents in China are to be avoid and I also think that Frank is not the best but also not the worst but a piece if a system, a system that sells and buys human beings! I heard that he helped many FT before and found them a secure teaching job in China.