mayanks

I don't know if someone has observed this, but if I append any random sub domain name, to a shortened url from bit.ly, it still takes me to the correct url.

For example, I picked up this from techrunch's tweet http://bit.ly/12V9c1. I could also create a link called http://mayanks.bit.ly/12V9c1 and it would still take me to techcrunch's site. So I get to brand my own short url.

Is this an undocumented feature or something is wrong here?

Couple of months ago, Techcrunch announced that it was going to use tcrn.ch as the domain name for it's shortened link. Their reasoning being that tcrn.ch will carry it's brand name in the shortened link as opposed to getting hidden in a bit.ly link. But lately I've observed that they seem to have gone back to bit.ly? Anyone has an idea why?