In attempting to perfect my presentation skills, I've realized that the lines between public and private speaking are nonexistent.
The difference is that a public speech has the opportunity to be a more polished version of your private speech, allowing you to craft and refine the truisms you communicate every day with your normal social network.
I saw Comedian after being referred to it by this great presentation zen blog post, and watching Jerry Seinfeld try to grow a new act from the ground up helped me see how communication is more than the distinction between public and private. Jerry knows how to build a comedy routine from years of working in the business, how to gauge reactions and adapt jokes, and the parallels to entrepreneurship are very useful.
Stand up comedians are entrepreneurs; they can gain a certain repute with one or two jokes, but in order to build a reputation worth paying for (in the eyes of their investors, the audience and the ticket sellers) they need to trial and error their way into a show.
Everyone has or can make a good joke. How many people take the time to build a system of jokes worth performing over and over again, and polish it until it looks professional and worth watching?