A few more things: 1) Be humble. Don't expect people to take it easy on you because you got street cred (You are a ruby contributor? You still need to show them how good you are at coding Ruby). Many people with creds get offended when they realize they are not as good as their credentials would imply. 2) Know yourself. Most candidates I've seen, including myself, encounter a moment in the interview where they get hi…
#1 does not make always sense to me. Open-source authors and contributors have their work out in the open. You can see their work, the way they interact with others online. Would you reject Guido van Rossum if he can't solve your whiteboard problem? Assuming he's suited for the job, his work speaks for itself.
And people lie on their resumes all the time. It's amazing how many outright lies we've caught when interviewing people (even those with "streed cred").