Twitter CEO Dick Costolo talked to the media today. He dropped some stats and some strategy notes. He says Twitter has 100 million active users, 40 percent of which don’t tweet but just follow. Fifty-five percent get to Twitter via mobile devices. Its product goals still key on simplicity, and it wants to surface content in a way that separates signal from noise. Hmmm. The company’s big business will be ads, including in-stream ads and hints of a distributed ad network. It doesn’t intend to build out data services or take an equity position in members of its ecosystem. I’d say those are all pretty solid strategies, and Twitter’s growth looks good. Nothing wrong with being a follow-only medium for many of its users. They’re still valuable advertising targets.