My wife has about twenty pairs of socks, and no more than a few of the pairs are the same variety. It's like some masochistic combinatorics problem every single time I fold socks. My kid and I literally were playing "sock go fish" a few times to get him to help (except ... I was more interested in the pairing, rather than taking turns. Doh.)

Laundry-folding happiness is increased significantly when I don't have to play "Find-the-mate" every time I pick up a sock (which applies to my kids' socks as well, since they are all patterned, but thankfully my son likes wearing party-colored socks, so I only need to match on shape).

I have two "vintages" of socks -- the old ones that I hate, and the newer ones that I prefer, roughly equally divided. I would donate + re-buy if I had more than two flavors of socks.