I have enough skills to create URL shortening service, but I don't this it is profitable. There are bunch of similar services for free.
http://adf.ly isn't just an URL shortening service. ( there are others like it )
It will advertise a website for 5 seconds ( and the website is paying adf.ly to be advertised )
The main difference from adf.ly and a common URL shortening service ( like goo.gl ), is that many forums/blogs/websites are using it will all their links!
They could use goo.gl ( example ), but they will not get any money from it.
Look at links in this blog: premiumhunt2012.blogspot.com ( I don't own it, it's just an example )
All links uses a linkbucks.com ( it's another service like adf.ly )
There are many other blog/forums that uses this kind of services.
I think that the main appeal that a service like adf.ly/linkbucks.com but with Bitcoin currency is that you will be able to pay "more" than others because of the lower fees in bitcoin transactions than paypal/alertpay.