what everyone has said - my examples of this:
OB (Oriental Breweries) got a license to make hoegaarden, budweiser and some other stuff in Gwangju, South Korea. the hoegaarden was always very good, its been a long time since I Had it there, but I recall it being basically as good as the real deal. the budweiser tasted VERY dry, noticeably different from american budweiser, which I was somewhat familiar with at the time I had it there.
labatt brewery in london, ontario got a license to brew a whole ton of stuff, but notably spaten and lowenbrau. spaten and lowenbrau are not the greatest pale lagers/"helles" made in germany, but what they do at labatt should be criminal. it tastes completely the same as a generic NAIL, something light labatt blue, or even verging on discount NAIL, but it comes in the lowenbrau/spaten cans. they are also 473ml instead of 500ml, a canada size pint (we LOVE getting ripped off in every way possible). it is nearly completely undrinkable swill.
a lot of people have emphasized megabrewers' skill in blending and making huge quantities of beer and keeping them consistent in taste. i never found that to be the case at all, and it was an unknown, since i don't know the storage time/conditions of these beers before I drank them, but I always found huge variation in many mega beers where one day it could be decent, the next completely terrible.