Did you ever stop and think...
All these people are here to see me... !
Not exactly stage fright, but a sudden pause as you realise that anything you say or do, good or bad, is somehow bigger than usual, because you're not talking to a couple of friends, you're not singing in the mirror. You have an impact because of the larger size of your audience.
It occurred to me a few minutes ago - everything I post here has a potential audience of over two million new people every month. That's over 70,000 per day!