I've been thinking about this topic myself and I think that there are three things that make alcohol of any kind particularly bad for someone struggling with their weight: 1. Calories. If you're not being careful, it's easy to drink heavy beers that have well over 150 calories each. Drink 6 and that's 900 calories. Prefer booze? A regular rum and coke doubles the calories per drink because of the sugar in the soda, so after 6 drinks you've ingested 1200 calories. Fancy drinks are even worse. Wine's probably best. 2. Munchies. It just seems to me that after a few drinks, my body wishes for something to soak it all up with. There's also an issue with impulse control and reduced inhibitions after getting tipsy. Whatever the reason, it seems that the drinks lead to extra food every time, so add at least 600 - 1000 more calories on top of the original calories. 3. Sedation. Though you might dance at first, alcohol will make you tired and hung over so that overall, you will want to move less than you would, burning fewer calories.
Guesonomics...I'm guessing that for every $50 - $100 you spend on alcohol, you gain at least 1 pound that you can't shake easily until you quit drinking for a while.