There are lots of ways different people in different professions might lose endorsement deals. An actor might lose some beer commercials if it turned out he was gay, or, worse, actually from Europe. A doctor probably wouldn't work as a spokesperson for Vioxx if he had, say, an inclination toward stabbing his patients in the chest. And a wine taster might lose his golden goose if people learned that he had no sense of smell and/or didn't go to graduate school.
Therefore, Jason Giambi has been fired by Nike. The good news? There's always a chance they'll remake RoboCop; he'd be perfect as the dude who falls in the toxic waste. Worst case, hey, he could find a job in one of their sweatshops.
Nike Severs Relationship With Giambi [ESPN.com]