[lucb1e]

Twitter/Facebook/whatever-the next-big-thing-is doesn't have 9 out of 10 fields that are on my ID card. If I show them a piece of blacked-out plastic with only my first name visible, since that's the only piece of information they have about me, it won't help them identify me.

Yes, you need to prove that you're the data subject matching their records before they should act on your request, whatever that request may be. But uploading a copy of your ID card almost never serves that purpose. See also a bigger comment I wrote elsewhere in this thread with sources and examples: https://news.ycombinator.com/item?id=23957503