Why would you want to make your own, when corporations have already spent billions of dollars perfecting their combinations of ingredients in products? http://www.healthboards.com/ubb/confused.gif I'd rather go with something that has been tested and would be more likely to be effective. Just my opinion.
I dunno...maybe for the same reason people still make their own bread and cookies So I can regulate how much I want...I don't want to pay a bunch of money just to get something with 2% of the ingredient that I want. Besides, don't you ever feel like you know more about yourself and what will work rather than a corporation hell bent on padding their executive pockets?
2% (salicylic) and 10% (BP) are as high as you'll get for facial preparations without a prescription. While I understand the feeling of, "but if I use MORE, my face will be CLEARER!" it's also very dangerous because you could strip the skin off your face, cause allergic reactions because of the higher dose, dry your face out dangerously, yadda yadda.
The only thing I've been able to find with a higher dosage of salicylic acid is wart remover. I know it sounds gross, but that's what they use to take those suckers off. It works, yes, but it dries the heck out of your skin for a couple of weeks. And when you're talking about the more-sensitive skin that's on the face, you're really risking scarring and other non-fun things.