Is it really necessary to carry a hydration pack or water bottles on a mountain bike ride, or can you just stop at a stream or puddle and refill your water bottle, saving weight and bulk on your bike, or are people just too paranoid about getting sick from untreated water, and if so, isnt that just a myth perpetuated by the hydration industry to sell more products, or can someone actually provide some evidence that drinking from a stream or puddle is more likely to make you sick than drinking from a tap or bottled water, and what about water purification tablets or filters, are they really effective or just another gimmick, and if you do need to carry a hydration system, whats the best type, bladder or bottles, and why.