Yes definitely

When I did the SQL 6.5 courses I was lucky enough to be taught by a trainer with commercial dba and they stressed the importance of this.

One thing I am not clear on. In SQL 6.5 you had to use sp_addalias to make logins impersonate dbo. SQL 7 seems to discourage this, and yet simply adding a login to the db_owner group seems to create these ownership issues.

How are you supposed to do it SQL 8 if you don't use sp_addalias?