Some airlines are getting stingy, I think, because I have also heard of people not getting a full can - just a little cup - as a matter of policy. I think it tends to happen on smaller budget airlines, but don't quote me on that, I've never had this problem, have only heard about it happening to others. In the case that's being referenced, it seems like a clear example of bigotry, though.
What can also sometimes happen is they will be low on pop, so they won't want to give out full cans, in order to be able to serve everyone on board. That has never happened to me - they always seem to plan well ahead and have enough for everyone. Usually what I do is ask for a "coke, no ice please", and they just hand me a can.
On the Alitalia flight to Poland 11 or so years ago, my dad asked about beer (after the initial 'free drink' serving period was over), and we were told to feel free to raid the cabinet.. So.. Yeah.. free beer! It wasn't even warm or anything. Not super cold, but it was well within acceptable beer drinking parameters.
On my LAN flights to Chile and my Air New Zealand flight to NZ, there was free unlimited wine for the duration of the relatively long flights. I want to say that the same thing was true for my flight to Peru, but I can't exactly remember.
My favourite airline to fly with so far - Air New Zealand. The customer service on board is .. amazing. You actually feel like a human when flying, and when you land in Auckland (in my case), the agents on the ground actually joke around with you and you continue feeling like a human for the whole experience. It was so refreshing - I recommend Air New Zealand to anyone, if it's an option. You will enjoy yourself.