I don't like it, but I had to do it.
From now on urlBorg will ask you to login if you want to create a short URL. The reason is that spammers took advantage of the URL shortening service to create short URLs they included in spam emails. As a result I got many complaints, I even have to pay $199 to GoDaddy (where the domain is registered) to
[...] cover the costs of responding to or "cleaning up" the outstanding spam complaints Go Daddy has received against your domain name so far. This fee is also used to cover the costs of processing future complaints, forwarding these complaints to you, and ensuring that the offending affiliates have been deleted. [...]
I still think GoDaddy is wrong to consider urlBorg part of the problem, but the truth is that even free on-line services should try to make the web a better and safer place. Authentication should make urlBorg spammer-unfriendly, or at least make it easier for me to fight them by disabling spam accounts and all their short URLs if necessary.
Requiring an account might be annoying to some, I understand. On the other hand, you can be sure all your short URLs are tracked and added to your profile (a feature that most urlBorg users like and depend on). Plus it will add some more "credibility" to any links starting with "ub0.cc".
Obviously, users just clicking on short URLs are not affected, this is for people using urlBorg to create short URLs.
API usage is not affected, either.