Doesn't really seem fair, does it?
Well, I dont know.
If you decide to run a company or a partnership or an aircraft together with others you accept collective responsibility and set in place checks and balances to ensure no single person acts alone on crucial matters. Love him, or hate him, it seems strange we all like to blame Sir Shred when he was but a single member of the Board, albeit the CEO. One wonders what the rest of the Board were doing?
However, you are unlikely to come unstuck if you have properly delegated your responsibility. If the maintenance organisation is qualified to do the work but an accident arises as a result of their neglect the liability will be theirs, albeit you may want to ask to see their liability insurance before you contract them to work on your aircraft.
Perhaps it doesnt seem fair when a member accepts command knowing his medical has lapsed; are we in greater danger by assuming some sort of collective responsibility for ensuring every pilot is "fit" to fly. These are inevitably the joys and pitfalls of group ownership and, as ever, the reasons you may want to wrap the excercise in a veil of limited liability - just in case.