10-15 minutes is no where near enough for most people with darker skin (ie. most of the world's population). I mean, fuck, I'm only olive skinned and I need at least 30 minutes to an hour at the most "dangerous" UV exposure at the highest levels to even begin to get the benefits. I don't start to get red skin until an hour or two and that's with no previous exposure (ie. coming out of winter). In the summer I can withstand 4 to 6 hours without my skin becoming red and 8 to 10 hours before I start to "burn". Darker complications have even longer times.
I assume by the moderation that most of slashdot is made up of minority pasty white cave-dweller homebodies with brain-damage caused by vitamin D and/or B12 deficiency. You are the abnormal outliers.
Thank you very much, dorks. There is a reason you're the outliers of the human race; please don't lock me in a cell and drain my superior blood for your nefarious purposes due to your weak genes, assholes.