Instagram announced today it has hit the 150 million user mark. The company has increased its user base by almost a third this year, as it boasted of 100 million users six months ago.

Instagram’s acquisition by Facebook in April 2012 doubtless helped fuel its growth, especially in markets outside the U.S. The company announced that over 60 percent users are from countries outside the U.S. Activity on Instagram has also increased, with over 55 million photos shared and 2 billion "likes," per day on the network.

And as long rumored, the company will apparently start selling advertising relatively soon—"within the next year," the Wall Street Journal reports. The newspaper notes that its big challenge will be to maintain Instagram’s “cool factor” while still making money.

Instagram caught some flack last year when it attempted to update its terms of service to include leasing user-generated images to advertisers; the company later backed off that change. Instagram’s parent company Facebook has generated its own controversy in recent weeks involving updates to its privacy policy, specifically its declaration that it will use profile information for advertising purposes. 

If and when Instagram decides to start generating revenue via advertising, it will have to maintain transparency around privacy concerns, something users might find more troubling than the platform's “cool factor.”