In the blog post announcing the changes (http://blog.instagram.com/post/38143346554/privacy-and-terms...), they called out a "few key updates." The changes to the TOS were described as, "Our updated terms of service help protect you, and prevent spam and abuse as we grow."

Our "friends" over there sure didn't go out of their way to call out an important change in the TOS. If it wasn't an attempt to sneak this by, it's indistinguishable from one.