It's been a rough couple of weeks for Instagram lurkers.

First, Instagram removed its infamous "following" tab, which let you surreptitiously keep track of what posts your friends were liking. Now, the company will no longer let you view more than a handful of photos on public profiles if you're not logged in.

Prior to the update, which was implemented in the last few weeks, anyone could browse public-facing profiles on Instagram via a browser without logging into the service. Now, after you scroll past the first dozen or so posts, Instagram will force a log-in you can't navigate away from.

Here's what it looks like:

Instagram now forces a log in after viewing a handful of photos. Image: screenshot / instagram

In a statement, a Facebook spokesperson confirmed the change.

"Now if you're not logged into Instagram, you can only see a certain amount of posts on public profiles before being asked to log in. This is to help people see photos on Instagram and then understand how to get the best Instagram experience by being part of the community, connecting and interacting with the people and things they love."

One one hand, it makes sense that Instagram would lock down its platform in this way. Facebook also greatly limits what content people can see without logging in. But it's a first for Instagram, which has historically been more open in what it makes visible to non-users.

As Instagram grows beyond its first billion users, tactics like this could help the service maintain growth. Forcing people to log in is also better for Instagram's advertising business. The service is reportedly trying to double the amount of advertising in the app amid fears from some Facebook executives that Instagram's growing popularity could hurt Facebook, which is still — for now — the company's main money maker.