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.

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?