If I tries to shorten the url of http://google.com several times, goo.gl always give back different result. I just wonder will goo.gl merge theses url together sometime later?
This interesting found implies how goo.gl is designed. They prefer writing directly to avoid duplication check and random seek caused by the check. And they though most of the urls are cold so it is not essential to merge them together to keep the hot cache small.
Or they assume nobody wants to play the system in this way. :-)
http://codepaste.net/48qfb7
But now I'll be able to shorten URL's with an official API rather than using a hack. I don't know why Google didn't make a public API from the start.