With the growing acceptance of Twitter into main stream use, the use of services to shorten lengthy URLs is growing. There are many of these free services out there on the web. Popular ones include:
First off, if someone is using a twitter application (for example Tweetdeck) any one clicking on a full and proper link it would appear as direct traffic. The only way to properly identify this users is to use your web analytics campaign tracking feature.
If someone were to click on a shorten URL on a web page, how the referrer is handled would vary by the both the shortening service (most service do however work the same way) and your web analytics software.
For example using tinyurl and generating a link to my company web site www.knechtology.com the shorten URL would appear as: http://tinyurl.com/dfjood and would generate the following sequence of hits.
GET 301 Redirect to http://www.knechtology.com/ http://tinyurl.com/dfjood
GET 200 text/html; charset=ISO-8859-1 http://www.knechtology.com/
The first hit might appear in tinyurl's web log files or possibly not depending on how they handle the 301 redirect. Regardless, there is nothing recorded in my web site's log files until the second hit.
Now the big question is: will this hit appear with the referrer of tinyurl.com or not. For that you need to check your log files. In my experience at best this will appear as a referrer from the shortening service. That's why if I'm posting a link in Twitter back to my web site, I alway like to add a campaign id to the URL.
I personally don't care which Tweet generated the traffic so here at K'nechtology have set up a standard one. If you want to distinguish your Tweets, you'll need to generate unique campaign IDs for each post.