Ninja Link lets you hide URLs. Just enter a link in the textbox on the web-site http:// www. ninjalink.com/ and you will get a link that points to ninjalink.com and automatically redirects to your link. This means that the visitors of your site won't know what the actual URL is until they visit the site.
That sounds new to me but I guess it's something not good. From the word ninja itself which we can relate it in real life, it's something an act of cheating or hiding something.
Try to read this article links: http://www.webuildpages.com/jim/link-bait-alone-wont-do-it-you-need-link-ninjas/ http://www.seomoz.org/blog/link-ninjas-vs-bait-pirates
Ninja Link allows you to hide your URLs. It's like Tinny url whic make yoru url short the visitors will not able to find actual url until they visit your webpage