I would guess Paul Allen, who has done work in Namibia. But take his anecdote with a grain of salt - plenty of journalists have misrepresented stories.

According to the Forbes list of billionaires: http://www.forbes.com/billionaires/list/#version:static_sear...

There are currently four Microsoft billionaires (probably fewer at the time referred to in the article):

* Bill Gates $79.2 B

* Steve Ballmer $21.5 B

* Paul Allen $17.5 B

* Charles Simonyi $1.4 B

paul allen

I would have guessed Balmer.

Paul Allen is well known to have one of the largest super-yachts in the world. I'm not sure Ballmer even has one.