Rockefeller literally put the "anti-trust" in "anti-trust law" when he created the Standard Oil Trust. Standard Oil's lawyer conceived of a scheme whereby shareholders put their shares into a Trust whose Trustees held the shares for their benefit. This scheme was widely imitated by other businesses to the point that the word "trust" was about as tainted at that time as the word "corporation" is in our own.
A trust, like a corporation, is not in and of itself illegal or immoral. However, both are legal devices which can be used to further nefarious ends.