Twitter was influenced by texting, which — group messaging aside — isn’t a big advertising platform. So it’s not surprising perhaps that despite its strong growth, Twitter still isn’t an advertising powerhouse. Part of the reason is the fear of killing the golden goose: Run too many ads and your users will flee to a competing service. But another reason is that the founders of Twitter want to invent something new. Slapping banner ads on Twitter.com clearly doesn’t have any appeal. -- Todd Wasserman