Richard Branson does things that matter to him ... for the sheer hell of it. Personally, I think that's a very legitimate career and business philosophy. Frankly, the reason that I take on new stuff, and keep accumulating frequent flyer miles, has long been the unadulterated joy I get from doing what I do, and the sheer pleasure from marching in the opposite direction from the crowd. The same was true, if I may admit it, to me as a builder/junior officer, age 23, in Vietnam in 1966+.
While Penelope Trunk (quoted by Guy Kawasaki) says:
The correlation between your happiness and your job is overrated. The most important factors, by far, are your optimism levels and your personal relationships. If you are a pessimist, a great job can’t overcome that. (Think of the jerks at the top.) And if you have great friends and family, you can probably be happy even if you hate your job (imagine a garbage collector who’s in love).
My guess is if you love what you do, chances are you belong to a minority compared with the rest of the workforce and will probably end up at Tom Peter-esque levels of success.
Other people will do well to follow Penelope's advice :-)