Yahoo (YHOO +1.5%) has 200M monthly mobile users, Marissa Mayer boasts at her Goldman presentation. Of course, a lot of those users are tied to pre-installed iOS apps, which don't feature ads. Mayer suggests Yahoo wants to offer 12-15 mobile apps, but adds it won't invest in maps "because I know from my past life how expensive that is." She sees "opportunities around original programming" (so do many others), thinks the success of Yahoo Sports "needs to be replicated," and insists the Microsoft (NASDAQ:MSFT) partnership is healthy, though room for improvement exists. (webcast) (live blog)