Interesting foresight that some have. According to their own blog, The 5 Point Cafe (a self-described dive bar) in Seattle, WA has already begun banning google glasses: http://the5pointcafe.com/google-glasses-banned/ .
This presents an interesting tension between the right for any private entity to define its own terms, and the expectation of privacy that one should (should not) enjoy in a ‘public’ space. i.e. to what extent is a ‘private’ bar a public space?