Personally, I don't have any problems w/how folks spend their disposable income. So if postman wants to use a Blue Tooth, cool. As long as I get my mail, I don't give a toss what he does. I mean, it's not like he's performing microsurgery whilst having a convo on his mobile, or driving a bus full of children.
I do think they look naff, however. They remind me of the Borg on 'Star Trek: the Next Generation'.