-I have mixed feelings on this question. Yes, the DM should have control over his/her campaign, but that should not stomp down on the player's fun. However, having a rules lawyer come up and tell the DM that he/she has to do all all this extra work, on top of what they're all ready doing, just because its in the rules, seems extremely disrespectful to me.
-I would have the option in the DMG, but make sure it's noted as optional and at the DM's discretion. Things like players wanting to own property, cohorts etc. should probably be discussed in-group prior to starting the campaign and not sprung on the DM when the players reach a high level.