Unfortunately we're pretty small and understaffed, so having what amounted to a skeleton crew on Fridays didn't work out. Clients weren't happy when they'd have to wait until Monday because the only person familiar with their project was off. My boss is very respectful about days off, but he often had no choice but to call someone in to handle an emergency. Employees would often switch their off days around (sometimes because they got called in, sometimes just because), so nobody ever really knew who would be around on any given Friday.
So it really depends on the size and nature of the business, in my experience.