The trend here (in California) is to serve filtered tap, which sometimes tastes better than regular tap water but is much more environmentally friendly than bottled. The machines for filtering are not cheap, and many restaurants are adding a couple of dollars as a water service charge to cover the cost, though many are also just providing the water for free. The machines can also add carbonation to the water, and that is also sometimes provided for free. I think it's a great trend.