We're talking about something as obvious as taking a photo and sending it to a friend in a streamlined fashion. If this counts as innovation here, I want no part in it. Taking a huge stream of data and figuring out what to show to who might be called an innovation, but this is not. Building the worlds best mapping service with street view is innovation, this is not.
It's taking a photo, which self-destructs after a certain period. It's not mind-blowingly innovative, but the idea, time periods (max of 10 secs) and even the UI involved are exactly the same as Snapchat.
If the original idea isn't innovative then Facebook's version is orders of magnitude less so.
I rarely defend Facebook, but if you make an app that snaps a photo (which self-destructs) that you can then send to friends, then you knew what you're getting yourself into. The only two options you have is to either make an app that is difficult to copy, or make an easy app but hope for the network effect to work in your favor (i.e. any social media thing out there).
On Internet forums accusations of "copying" are generally used the same as "stealing" with a morality payload attached. For example, when something is copied and slightly modified people say "fork" to make sure it is read positively. shrug
Well, I think this is assumed, yes. But Facebook would never admit that "Yes, we liked this idea, so we developed our own" - and because of this it shows a feeling of guilt, or at minimum not being honest. But that fits with Facebook's character, and many who are dishonest in fact.
The UX is identical. Self-destructing, the UI for choosing friends / viewing photos / taking photos is the same. The fact that it notifies the user if a screenshot is taken... it's the same. Facebook added nothing new, only copied.