Vitamin C is fairly benign - nobody has ever died from vitamin C over-consumption. Based on rat studies, the toxic dose is likely over 11g/kg body weight. So, maybe 700,000 mg per day?Can someone tell me when Vit C becomes toxic. 10,000 mgs sounds excessive.
That doesn't mean high vitamin C intake doesn't have side effects. Gas, bloating, nausea, and diarrhea are common in doses above 2000 mg/day - usually these taper off as your body gets used to it.
There is a link between vitamin C and kidney stones (as the article said) but it's not clear who is at risk... In general, most people have no serious issues.