It's a hack because Instagram doesn't give you an option to license under CC in their interface, and it's doubtful they will, now that they're owned by FB. CC licensing on Flickr has had a huge impact on the free culture movement, and it'd be great to see something like that happen with Instagram, which is now (I assume) orders of magnitude more popular.
The way the default licensing on Instagram works is: you hold copyright and Instagram has a non-exclusive right to use them in some ways. It doesn't permit usage outside of that. So if you wanted to use an image on your blog or in a Wikipedia article you'd be out of luck (or maybe just get lucky and not get in any trouble).
The way the default licensing on Instagram works is: you hold copyright and Instagram has a non-exclusive right to use them in some ways. It doesn't permit usage outside of that. So if you wanted to use an image on your blog or in a Wikipedia article you'd be out of luck (or maybe just get lucky and not get in any trouble).