as i said earlier, i can get 10 mpg in any car - it depends on *how* you drive it.
I drive a BMW M3 and it gets <25 mpg on highway and probably about 15 in city. YET, i drive very infrequently as i am blessed with the ability to telecommute every day. even so, i live about 1.5 miles from work so i can't even get through one song on the radio. it takes me about 1-2 months to go through a tank of gas = $40-50. Of course on the weekends, i might take longer trips, etc. i'm lucky and in a different circumstance from most. my reasoning for the car is that i've always liked performance oriented cars. big cars are not interesting *to me* but i'm not going to tell others that they can't have such cars.
does this mean that i'm overcompensating for some insecurities? i don't look at it that way. my reasoning is that i want to have 'fun' when i'm driving. i love going fast on the twisties because it's 'thrilling'. so what's wrong with doing this as long as it is done responsibly? if anything, i'm overcompensating for boring commutes.
others have said that they don't have cars and use public transportation. public transportation is great - if you have it. tell that to a guy who lives in suburbs or more rural areas and there are lots of these cases in the US. I totally understand not needing a car in a city but then explain how you get groceries, do your shopping for larger items, etc. i imagine you might make many separate trips, or just buy groceries for the day or two. how do you carry a case of beer home - this would get heavy after a few blocks.