So say you hire me to build you an online community.
I do my job well, I build relationships with the key members, tighten the group around me and you pay my invoices on time.
Then one day something goes wrong.
Maybe you pay an invoice late, or I want to up my rates. Does your community belong to you and me? Can you stop me from using my relationships and emigrating with your community? Maybe to your competitors?
It's a predicament. If you don't get involved, you could be in trouble.
So it's best to take an interest. Make sure you get the consultancy, as well as the labour, from your community manager. Why not ask her "so who are the key members?" and drop them a nice e-mail from time to time? Discounts, sneak previews and fancy offers work well.
If you wouldn't give one salesman responsibility for all your big accounts, why would you give your community manager entire responsibility for your community?