The more likely 'law' is that you are feeling nervous because you know there are several points of failure in your demo that you haven't taken care of.

I'll always remember as a first-year CS undergrad our professor came into class one day and told us about how he just came out of an interview with this recently minted Phd for an associate professor position.

The candidate's demo just totally crashed and burned and he was a wreck for the rest of the interview.

Since then I've developed a fundamental fear of live demos. Rarely is the cost/benefit worth it over a pre-recorded demo.

being able to say this is my real, live production site and demoing it is pretty valuable.

To this day I don't know if it was Skype of my old T43. Most likely the latter.

Murphies law?

But it is pretty ballsy to assume that Skype works - who is to say that the there is wireless internet there?

Who is to say that Skype will ever work, even when connected to a 100% reliable wired source?

I love Skype, but I always get really nervous when it becomes a required part of any interaction. It's just too shaky for that.