I have long entertained gossip from self-proclaimed "beer connoisseurs" that the Guiness I am drinking is not really brewed in Ireland, nor the Beck's from Germany.
I would imagine that where you are in the world really does determine where your particular bottle of macro brand X was bottled, so my question is how can you determine the true origin of the bottle -- can you trust the location on the bottle next to "brewed and bottled by..."?