Observation

Have you noticed that being "up for something" and being "down for something" means the same thing?  Considering up and down are polar opposites, I find this odd.  Never thought about it?  Allow me to demonstrate with two different hypothetical conversations:

1)    J Woww: Do you want to go shopping for animal print dresses that are 2 sizes too small?
       Snookie: I'm totally up for that.  And then we can smush.

2)    Timmy: Hey, do you want some chronic?
       Snoop Dogg: Yea man, I'm down with that.

Just something I was thinking about...