Whether you get a hangover or not is dependent on pretty much all the variables of alcohol metabolism: how much you drink, how fast, at what time, whether you had a full stomach, what type of food you ate, the type of alcohol (dark vs clear), whether you smoked cigarettes, etc. While you definitely shouldn't drink so much, I think it's a bit disingenuous to simply the issue down to how much you drank the night before.
(My personal theory for the two beers night is due to me drinking them some time between 1 and 3 in the morning.)
You can drink a fairly extreme amounts of alcohol and not get a hangover if you also drink enough water before you go to sleep. Alternatively, if you where even slightly dehydrated even fairly modest drinking can result in a hangover.
I'm glad I get hangovers. It makes it really obvious when I've overdone it, and it's a useful reminder not to do that again. If I could drink a lot all the time and never experience the short term negative effects then I would definitely experience the long-term ones of alcoholism.