Wow there are some great examples here.. I think some of you guys need to drop those friends!
I have a similar situation where another couple invited my wife and I out for sushi. We agreed, but found out once we were in the car that we were going to a high-end sushi bar downtown which is very expensive. That's fine, my wife and I could just order less and still have fun with the company of our friends.
My wife and I ordered conservatively, but still enjoyed our meal.. ended up spending $51 total between the 2 of us. I saw a coworker across the restaurant and went to say hello, during which time the bill came and the other couple just said "split it on both cards" to the waiter. My wife was too shy to speak up, so we ended up paying $100! Our friends had several glasses of wine, several large platters of food, and just went all out, spending almost $150. My wife told me on the way home that had happened. I'm not ever going to bring it up with the friend, but I'm definitely not going to dinner with them again. In the end, my timing to walk away from the table was poor, my wife should have spoken up, and my friend knew exactly what he was doing when he sadi "split the bill". Oh well - live and learn.
Keep the stories coming!