It's definitely done. A traditional method is that the longer you've been at a place, the more vacation you earn. Another technique I've seen is to have a divide, eg "VP and above get an extra 5 days per year."
Facebook, Google, etc commonly use the contractor technique, where anyone you want to work for you but not give benefits becomes an independent contractor, or works for a vendor. Eg, the cooks in the Facebook kitchens.
Yeah - I've seen tiered vacation days based on seniority, but I'm wondering specifically about giving some folks unlimited and others a prescribed number of days. That seems to straddle an almost philosophical issue.
Facebook, Google, etc commonly use the contractor technique, where anyone you want to work for you but not give benefits becomes an independent contractor, or works for a vendor. Eg, the cooks in the Facebook kitchens.