Hopefully surprising no one, Facebook plans to put ads in once the platform is big enough:
“Kevin [Systrom] has always been clear that we’re building Instagram to be a business,” Zuckerberg said. “We expect over time to generate a lot of profit from it. We think the right focus for now is to continue increasing the footprint of Instagram and, when the right time comes, we’ll think about advertising.”
When they do this, they should also offer a $5/year pro plan to not see ads. And that's it. Just a little button that takes $5 from your Facebook widget bank account thing 1 a year so you don't have to see ads.
I'm not saying every internet thing has to charge money to be successful. Just give folks an option to pay you and not default to ads as the only way.