Even if domains are just a loss leader for GoDaddy, they surely look at their numbers, so this is a way to send them a message they'll hear. Maybe it will work, maybe it won't, but no one who still has a domain at GoDaddy will be entitled to complain about SOPA if it passes.
I'm going to piggyback on your comment here, since it's at the top of the comment thread. From the Reddit link: "Name Cheap messaged me with a special discount code for reddit users: BYEBYEGD I'm not taking any positions i'm just reporting it. I asked him to give reddit users a better deal." I'm not affiliated with NameCheap at all, but if you're going to move your domain, this might make things easier.
Is this about scammers flocking to NameCheap because it's, well, cheap? Or is NameCheap somehow marketing to spammers while trying to maintain plausible deniability? I'd be happy to consider moving my sites over to NameCheap, but I don't want to move from one evil registrar to another registrar.