A little devil's avocate: Isn't Instagram primarily a photo sharing app? I'm not sure why people are complaining that it starts the upload on filter completion. My only question is how long are photos not marked as user initiated uploads kept?
To me this seems way offside. What if I, a regular user, uses instagram for taking all my photos. What if I take nude photos of my wife. Should I really expect instagram to upload them without my permission? I'm guessing 99% of people would not only be surprised by this behavior, but also outraged.
If your intention was in fact to upload the photo, good on you, you save a few precious seconds. If your intention was not to upload the photo, then they simply cut the connection, send a delete order and move on.