tldr addendum: because they want to push back some of the 99% of registered sites that use the free DNS service yet drive huge amounts of traffic and want them to upgrade to DNS Premium support.

"GoDaddy have decided to block DNS traffic rather then invest in their infrastructure to handle the additional load"

The article doesn't say that at all, it specifically mentions that this is not the reason for the block. Did you read it before commenting?

Yeah, I did, but I accidentally included information from the "GoDaddy response" linked by rednaught. If you didn't read the 2nd link, then I understand how it sounds wrong. In retrospect, I should have replied to rednaught's post.