As anyone who reads much of my site knows, I'm not a fan of how RFID is being implemented. However, I'm not against the technology itself as it has many practical uses. For example, some hotels have begun putting washable RFID in the towels and bathrobes to keep people from stealing them.
Since the RFID towels have no privacy invading purpose at all and serve deter self-entitled punks who think it's ok to take hotel items, I will offer my tentative support for this. The main concern is feature creep meaning that depending how they implement this, they may also know which towels you used and when. I can't really see the hotels bothering to do so, but if they did, that would be crossing the line big time.
Source: http://intransit.blogs.nytimes.com/2011/04/11/gee-how-did-that-towel-end-up-in-my-suitcase/ (H/T to The Consumerist for the link)