It's less of a salaried work issue, it's more one of people not knowing or not caring about their rights. I can't talk about the US landscape but in germany unlimited unpaid overtime is not legal, still you see that often in work contracts, especially in contracts in startups and web/multimedia agencies. Its especially common where unions and other organizations that could enforce legal limits are weak. I've for example never seen such a clause (and unpaid overtime) in organizations where a strong worker rights position existed.
