Would you ever SWING!!?

Ok so a friend of mine just recently told me that her and her husband are swingers, how could I have never known this?? I thought we were really close but I guess I don't know her as well as I thought. She said they had a foursome with a random couple they met at a bar the other night, and couldn't wait to get home so they did it a van parked outside. How crazy is that. Not that it was her first time, she said sometimes they swap, while they're in the same room. Sometimes it's her and another couple while her husband watches! How could she keep something like this from me for two years? Im not someone to judge, to each their own. Do you know anybody whose ever done this?? She said it's more common than I think and it must be if they pick up partners just about everytime they go out. Is it really that common?? Are there lots of swingers now adays? Would you ever consider it?