It's discrimination if you're a Butt Pirate out trying to find the brown treasure hole.
For the rest of us single men ladies night is great. Women get in free, get drunk free, and we get to reap the benefits of it. I've got a place I hit every Weds. night. There's easily a 3/1 woman to man ratio. Chicks drink free until midnight so I usually start hunting about 11.