There's a lot of talk about printing boarding cards and indeed I see many people at airports waving around their printed andcrinkled A4-sheets. I've always thought of this as a temporary work-around rather than a solution - and indeed, I've not printed a boarding pass in years I think - apart from flights to exotic destinations. I fly weekly as a passenger, mostly within Germany, sometimes Europe.
I usually check-in online via smartphone and to me, this is no more and less than picking my seat. And indeed I've wondered may times why I can only do this 24 h before the flight. The boarding pass gets issued within the app (or sent to the passbook app on the iPhone, to be instantly ON the home screen in due time for the flight). Why do people print?
As to claiming for delayed flights you were not on, you do still have to present your boarding pass (bar code) and that says who actually turned up at the airport. Unless, I'm missing something?
There is no connection whatsoever between me having a boarding pass/bar code and me being at the airport.
Don't often travel outside Europe, so visas aren't usually an issue, but passport and/or ID checks are done at gate, unless you are checking baggage with a human being.
Apart from the immigration checks (which have nothing to with the airline) there are usually no ID checks involved in boarding an airplane here. I remember AirFrance does it and I've always wondered what for. On Lufthansa and AirBerlin and the likes, I can let anyone fly on my boarding pass, it's not of the airline's concern who that person actually is... (Doesn't apply to flights to the US, obviously).