CNN's John Sutter spoke with Mailchimp CEO Eric Schmidt about his new book, Clear versus Clever. He says the company is trying to strike a balance between being clever and delighting its users in ways that are appropriate for today's world. But it can get out of hand if you don't know what your audience wants or when they're going to interact with an email message - such as Google's April Fool's Day joke this year. "Cleverness is advanced level stuff; aiming for delight can cause the most problems"