The article below is a great post over on the Force.com blogs about record ownership. I know many people have talked about and do have one 'user' account that owns most or all records such as accounts in some orgs, maybe a 'ABC Co. Sales Systems' user. This usually stems from needing a user account for integrations, and this is the user account that is chosen to generate the accounts through some API service. The problem is that the accounts oftentimes are never reassigned to a real user. The blog post discusses some of the transaction costs associated with this model, especially in larger organizations and how to deal with it. Give it a read!