Think of Glass as a new sense instead of a machine. The sense of information. The phone was just a clumsy prosthesis that was a pain to use. Most of what we sense is also "useless". We filter. If sight required us to pull a weird little periscope out of our pocket every time we wanted to do it, it would look like a strange addiction as well.

Surely there's a case to be made for sensory overload for this new sense, especially as people become accustomed to it. "Why do my eyes hurt? -- You've never used them before."