How safe are ETF's?

Chaps, how safe do you think ETF's are ?

I don't mean in terms of protection from market decline - obviously the ETF rises and falls the with market.

I mean is there a chance of the ETF manager suddenly going belly up because of some dreadful thing they did which was not related to the underlying investments, and then shareholders finding their money goes down the gurgler. The sort of things I'm thinking of are SSgA as a corporate vehicle doing something unwise, and everyone goes down with the ship.

Compare this to, as I understand it, the situation with a trust where the assets are owned by the trust and the unit holders own a portion of the assets held in the trust. The management company is separate, and if the manager puts his hand on his secretary's knee and gets sued for harassment, or if the manager does something else stoopid and implodes, then AIUI the unit holders assets are preserved.

Thanks in advance if anyone knows.