Our house is a very, very fine house: What about Them Slytherins?

thelastgoodname and I have recently been talking about Harry Potter, as we are wont to do from time to time, and I wanted to get your perspective on some of the things we've been talking about.

( Cut for stream-of-consciousness discussion of gender, class, Houses, and the awesomeness of Molly Weasley )

So, to recap in case that was too large a herd of teal deer for you:

1. How does class function in the Potterverse? Are the Malfoys old money or nouvea riche? Why do Wizards need money away? Can't they pretty much magic up whatever they want?
2. What does it mean when the Sorting Hat sorts you into Slytherin? Why do none of the Slytherins stay and fight at the Battle of Hogwarts? Why do none of the other Houses (with the exception of Gryffindor with Peter Pettigrew) contain Death Eaters?
3. Finally, and most importantly, how much do you love Molly Weasley? What do you think her involvement was in the First War?