I do 5 A levels (Maths, FM, Economics, Physics and CompSci) with only mediocre GCSE results. It certainly doesn't take a genius to do 5, it's just a question of whether you want to do so. I think that it is a bad idea overall, but the situation my school put me in meant I kind of had to, or otherwise 2 term's worth of work would've gone down the drain.
Unless you LOVE all 5 of your subjects, it is not worthwhile.
Btw, I don't have a job or a social life, but I made the decision to do my best in a levels regardless, i.e I would be in the same position even if I did only 3 (I always question friends who complain about their workload, yet spend 10+ hours a week stacking shelves just to fill up their cars).