I came up with a solution to this. My DH does fine sorting his socks. My older DS does his own laundry and doesn't have many sock issues. My younger DS is another story. He's been coming and going for the past 5 or so years (college, summer job out-of-state, recently moved to yet another state). Whenever he comes home, he leaves behind orphan socks. I find them under his bed, in his hamper, in the bathroom, etc. He just spent two weeks here and his socks seemed to multiply.
My solution - I put them in a pile as I find them. When they're all rounded up, I match as many pairs as I can. Whatever is left hits the trash. No mercy. It's simple and effective!