Comment 64 for bug 1160365

+1 for partner_id + contact_id

For me it is very important to have one clear partner field that is the "legal commercial part" (it can be company or not)

For the contact_id it is just a person at a time that represent this company, but this person/contact change and is just for communication (like partner_ids on meetings and so).

All my cutomers understand that you have a customer part and one or more contacts for this customer. If you only want one field, remove contact on business document and use openchatter to communicate.