It's official. According to an article posted last month on Coaster.net
Knott's Soak City Waterpark in Buena Park, CA will weigh riders on it's Pacific Spin slide. According to the article this is in response to orders from Cal-OSHA which found that several incidents were caused by overweight rafts. It appears that the weighing will be done by group (not individuals).
Certainly there's been talk of weight requirements for a while, but is this finally something that's going to become the norm? One industry consultant that I spoke with said some slide manufacturers are planning to develop new products that include scales.