My hair algae didn't go away in my 65 until I increased the flow to 15x's an hour. Now I'm at 20x and still have room for more flow. As long as the flow is spread out and randomized, and like Johnny said, not blasting your corals, I don't think you can have too much flow.
Lots of well-placed flow is great for the tank, as it brings food to corals and keeps them clean, and also keeps dissolved organic compounds in suspension for the skimmer to take care of.