Also this does not means if anyone create self-moderated thread for a service / ANN , then his motive behind is to scam.
I agree with @tranthidung, enabling non-self-moderated thread to self-moderated thread would help scammer to hide his evil activity
One of this example is Sudoku wallet, I never think this project become scam since the dev/team is responsible to solve the bug or problem from his customer, also they have run signature campaign for 4 weeks. But now this project become scam since there's one victim complain in their ANN [1]. Fortunately the thread is non-self-moderated thread, so he can't delete any users post.
[1] https://bitcointalksearch.org/topic/ann-sudoku-wallet-bitcoin-tumbler-coinjoin-instantly-mixing-5194344