My understanding from a recent discussion with a Mingle360 rep is that they expect sponsors & advertisers to purchase the device, not individuals. E.g., Company X sponsors MingleSticks for everyone at a convention, club, gallery, etc. – and, in return, gets exclusive advertising rights on the users' Mingle360 web portal for a designated period of time.
What bothers me most about people using Facebook and the like for 'important' messages is that Facebook is still, for most people, a destination more than a platform. An analog metaphor would be posting a note in the town square vs. sending you a letter in the mail. As a social person, you may frequent the town square to read and send messages – but it's still an indirect form of contact. Many people have SMS/email forwarding enabled for Facebook messages, but that's certainly not a given.