How Big of a Platform Does an Author Need?

Agent Chip MacGregor has been doing a question and answer session on his blog. I really appreciate him doing this and I’m learning from each segment he does. Recently he got this question: How big of a plaform does an author need?

I know many agents are looking for an author to have a big “platform.” What does a big platform look like to you?

Chip answers:

“A platform is a number. You speak? How many people do you speak to over the course of a year? You write a column? What’s your readership? Yo...