I have come across several companies that create contact records for people who are also users. Typically this is because they want internal contact data to synch with their Outlook contacts and their mobile phones. The problem is that if you have email addresses on both contacts and users, appointments tracked by those users will disappear from their calendars and there will be email tracking issues.

I think a good improvement would be to somehow allow user data to be synched with Outlook contacts—either allow local data synch rules for user records, or have some way to classify a contact as an internal contact and have the email and appointment synch process not conflict these addresses with user addresses.