Dear JoshuaZ, regarding this:

"Consider the uploaded individual that decides to turn the entire planet into computronium or worse, turn the solar system into a Matrioshka brain. People opt out of that how?"

I consider such a premise to be so unlikely it is impossible. It is a very silly premise for three reasons.

1. Destroying the entire planet when there is a whole universe full of matter is insane. If insane people exist in the future post-intelligence-explosion upload-world then insane people will be dealt with thus no danger but insanity post-intelligence-explosion will be impossible, insanity is a consequence of stupidity, insanity will be extinct in the future.

2. Earth destructive actions are stupid: see above explanation regarding insanity: it also explains how stupidity will be obsolete.

3. People opt out by stating they want to opt out. I'm sure an email will suffice.

It isn't obvious to me that all wars stem from resource scarcity.

Sorry that it isn't obvious how scarcity causes war. I don't have time to explain so I will leave you with some consensual validation regarding Ray Kurzweil who seems to think the war-scarcity interrelationship is obvious:

"I've actually grown up with a history of scarcity — and wars and conflict come from scarcity — but information is quite the opposite of that." ~ Ray Kurzweil http://www.hollywoodreporter.com/risky-business/sxsw-2012-damon-lindelof-ray-kurzweil-297218