This is the eternal question, "Is the beer belly a myth?" The answer is not clear. Recently, researchers at the University of Copenhagen tried to answer this question. They conducted a review of all scientific literature concerning abdominal and general obesity and beer consumption. Their findings were mixed. French women who drank beer had a bigger waist-to-hip ratio (WHR), while this
occurred in German in Czech men only. Overall, there was no conclusive correlation between beer drinking and obesity. It appears that volume and frequency of beer consumption appear to play a role in weight gain. Men who drank more than 4 litres per week tended to have more abdominal obesity. Drinking frequency also played a role in obesity. They found that frequency of drinking was inversely related to weight gain. This means that binge drinkers were more likely to be overweight than those that consumed the same amount of alcohol daily. There was little evidence than moderate beer consumption, less than 500ml/day, caused beer bellies.
The researchers has a couple of thoughts about why beer drinking might be associated with weight gain. Firstly, in some populations beer drinkers have poorer diets than other beverage drinkers. In the US population, drinking beer was associated with higher energy intakes and reduced intake of fruits and veggies. This was in comparison to wine drinkers.
Secondly, beer drinking is associated with smoking. Something else that has been associated with weight gain. The association with exercise and beer drinkers was mixed. Beer intake was greater in college athletes than lazy students. 
So there you have it: science says you will not get fat by drinking a daily pint. Just don't smoke, stay away from the chicken wings and get some exercise.