I'm starting to believe this complaint just stems from people that don't actually want to take vacation and are just upset because they don't get an extra fistful of cash.

I work for a startup with unlimited vacation and know several others that do as well. Anyone who wants to take a vacation can take it at almost any time and for weeks at a time - no questions asked. The only time I've ever seen any conflict is when there was a major release planned at the same time as the beginning of one vacation, in which case the employee just pushed it back a few days.