I don't think of Twitter as a social network. I think of it as a messaging system that has a lot of social components to it.

I knew Mac pretty well. I'd used them when I was younger.

When you think of a social network, you have these two-way interactions: "Are you my friend? Yes? No? Yes?" Like LinkedIn, it's business oriented, but it's all about establishing connections. You connect to me through my other connections, and that sort of thing, and you sort of define who your friends are. Twitter doesn't have that.

Have confidence in your ideas before they even exist.

I started as an artist and I had a side job moving some heavy boxes for a publishing company. They had just gotten a Mac for their art department, the department that creates the book covers. I was kind of showing the art director a thing or two about how to use a Mac. And one day everyone went out to lunch and I jumped on the computer and designed a book jacket and slipped it in the pile to go to the review board in New York. They picked my jacket and when the art director got back to Boston, he wanted to know who designed it and I said, "Me." He was like, "The box guy?"

When I studied graphic design, I learned a valuable lesson: There's no perfect answer to the puzzle, and creativity is a renewable resource.

Willingness to take risks is the path to success.