Comment 1 for bug 60364

See also 3958
Stuart explained there that deleting accounts would break some constraints. We would leave bugs unassigned, unowned products, etc.
I'd suggest that part of the workflow of deleting an account could be a page showing all the stuff that needs to be delegated before leaving LP.

Something like:
"Since you're deleting your account you need to re-assign {bug, branch, product} to someone else before complete removal."