I think these unlimited PTO companies are being disingenuous. I am sure it is nice to have as much time off as you want, but in reality you aren't going to take more than 4 weeks off. If I was an employer of this type and I saw employees taking off more time than that, I would recognize that they must not have enough to do and less people could probably do the same amount of work.

In reality, these types of companies are trying to position themselves as the 'Cool' kid on the block who cares more about their employees, a la Google and all the new tech companies. It isn't predatory or being a slave task master to set a defined limit of time off and expect employees to work for what they are being paid to do. The trick is to make sure employees are given every opportunity to use their PTO without making them feel guilty for doing so.