visionmedia/debug — pull request #38 by slaskis (2013-01-31 16:48:50+00:00)
Title: Mobile Safari (private mode) is broken with debug

Mobile Safari has a dumb feature where it goes ahead and throws an exception when trying to access the localStorage in private mode.

Other people with the same issue:
http://meta.stackoverflow.com/questions/123116/safari-5-1-2-log-in-doesnt-work

Simply wrapping the local storage access in a try/catch should do the trick...