I think one reason why a lot of people are hesitant to charge money is that it completely alters the relationship with your users. Paying customers deserve a much higher level of service than free users.

This is probably just another good reason to charge though. Taking other people's money is a commitment to providing service to them in exchange. You can't have too many good reasons not to give up.

Making money at a startup and having fun are (thankfully) not mutually exclusive.

One could argue that the more revenues you get, the more fun a startup is.

If you're not making money (or at least planning to make money), it's not a startup. It's a hobby.

Unfortuneately that seems to be needed to be pointed out.

Why do people insist on calling things startups when it is just a cool app that will never make any money?

"Business isn’t a game, and I think some web entrepreneurs treat it that way."

I like to think of it as a game, a fun problem to explore. Helps to keep thinking fresh and flexible. Just a matter of defining appropriate conditions of success and failure (which may itself be a part of the game ;).

I am really enjoying these weekly posts, but I was hoping to hear a little more about the YC summer session. For example, who spoke this week?