i dropped out at easter in my first year. 
if it helps, i'm a fully functioning adult who went back to uni as a mature student after a period of time in the workplace (6 or 7 years). then i went on to a masters. and i'm considering phd.
oh, and when i dropped out, my parents made a doctors appointment for me, because they wanted officila verification that i wasn't mental. (their words).
i worked in a series of fairly shit shop jobs for a year, took a temp job as a civil servant, then joined the raf as an officer. (studied since leaving).
you know - if it is the social side, he's going to have the same problems with work.
where is he now? presumably he is financially dependent on you at the mo? so the whole 'oh, i'm going to live in a bedsit' routine is going to come crashing down round this ears without him finding and keeping a job?
i suggest (like others) doing nothing but be supportive-ish. if he wants to make adult decisions, that's fine (to be fair - he's going to have to that anyway, as he's moving away and getting himself a job). uni isn't the be all and end all, and quite often those who drop out early do go back to it when they are a - ready, and b- see the benefit.
i imagine spending a year in a bed sit on minimum wage will be enough to crystallise the benefit of education. you'll have to watch for the depression, but there's not a lot you can do at the moment because he is probably a bit disappointed with himself/ mixed up about where he's going.
tough for you though, but at the mo you have to respect the fact that they are his options, not yours. hard, hard, hard. 