One wrinkle to this is that it is quite possible to become passionate about something which is initially a grind, at which point the state described in the article of it not feeling like work would kick in. In fact there are several successful entrepreneurs out there (eg. Mark Cuban) who openly advocate passion following work rather than the other way round.

If you do know of something which doesn't feel like work to you, but does feel like work to everybody else, there's indeed probably something there. But if you don't, it may be possible to create such a something...