Well... when you look at the org chart of many companies, the answer is obvious. Either there is no person responsible for anything at all, and everyone works for themselves, or there are dozens of little fiefdoms, competing for budget, staff and anything else.
But it's rare these days to have one person or even a committee that actually takes responsibility for a product as a whole and most importantly has a joint, shared and agreed-upon vision: how should the product look like, what should the product accomplish and how should the product be architected?