I think we all have different employment systems so there is a lot of confusion on this thread. I don't and have never gotten additional compensation or comp time or even explicit bonus promise for working overtime and have always held jobs where overtime is assumed. It's assumed to just be baked into the high pay. Then I get certain amount of vacation and sick time, which are never fully used because the implicit assumption is you are working too hard to use it all and the deadlines are set accordingly. The only difference is that one type of compensation may accrue a balance and one type may not, or that you might get capped out on vacation and then be unable to use sick. So in a situation where the employee has been worked to exhaustion, it is preferable to use sick leave to recover to save vacation for some time where you are doing something more fun that recovering from being worked to exhaustion. I have never had an employer who has expressed any concerns about that whatsoever, even the biggest baddest hardass New York real estate finance senior partners, so the fact that some people are describing this as fraud leads me to believe there is just some sort of cultural or legal disconnect here.
There also seems to be the assumption that people can just work 12-16 hours a day for months on end and be totally perfectly healthy with no ill effects. I have never seen that happen, although maybe you all are some sort of supermen and all the high finance workaholics I used to hang with just have weak constitutions or something. Maybe these are different sort of jobs, where the hours are less intense and involve a lot of sitting and waiting or pointless meetings or where people really aren't doing much work and are just sort of wildly exaggerating. If your 80 hour week involves constantly tracking your time, constantly under a deadline, working through breakfast, lunch, dinner, etc., pushing through exhaustion and illness, it is literally hellish and most people break, mentally or physically, at some point along the way and the question is just how long you last (2 years, 4 years, 8 years).
I think we all brought different assumptions to this thread. But here's some advice from the "sick leave" side of the argument -- if someone works 80 hours a week to make you money, you better be really careful before accusing them of fraud over what may actually be different cultural expectations. That would be a "fuck you take this job and shove it" moment for me.