[willcipriano]

The minimum wage always applies, so you'd have to pay at least [168 * $7.25] $1218 per week if you wanted someone to work 24/7 365. Had the minimum wage kept up with inflation that would've been somewhat of a limiting factor. The primary limiting factor is "at will employment", that is a doctrine where you do not owe your employer any notice when you wish to leave your job. So if they tell you "Work 100 hours a week" you can tell them "no" and leave without legal consequences. In practice there is a informal understanding that you will provide a employer with two weeks notice when you leave, and they will often give you a poor professional reference if you do not oblige them.

Another wrinkle is most workers aren't really aware of the legalities of salaried work, you'll see people making statements like the OP here about "company time" for example. Originally the arrangement was designed for people like CEOs and executives of companies where it wouldn't make sense to track hours as they had a stake in the company, but it has been expanded mostly to side step things like mandatory overtime pay.