Facebook says that there are no plans for now to add advertising to Instagram, even though advertisers are approaching them, CEO Mark Zuckerberg said today during the company’s Q1 earnings call. Adding ads could end up stunting Instagram’s rapid growth. He said, more than once during the call, that Instagram is currently growing at a faster rate than FB did at the same age, and it now has 100 million users. “They’re really doing well and growing quickly and that is the right focus for them,” Zuckerberg said. “They have the opportunity to…build community. I am really optimistic about the business and the opportunities.” But he also noted that “big brands are approaching us” about doing more on the platform — perhaps commercializing more, is the implication here. Instagram is already a pretty substantial marketing platform.