I used to work at a company that had no fixed hours... I usually spent at least 10 hours a day on the weekdays and often stopped in on the weekends and there was usually at least a smattering of people there, and collaboration and morale were both high. They really got it right on that one. Then investors started courting the company, and management started telling people they wanted butts in seats at 9:30am. Well as soon as 5:30 rolls around it became a ghost town.