True for IRAs, but if you self-direct an ERISA plan you don't need a third party custodian. In either case, the group I am dealing with within MFG claims the personal guaranty is signed as a matter of course. I have also spoken with people at several IRA custodians such as Millenium who have confirmed that many of their clients also signed such a guaranty with MFG, but that it is a prohibited transaction. One custodian said that I was the first person to bring it to their attention and they will watch out for it from now on.
Tom