Internal referer tracking is important to have real-time information where your traffic is coming from.  We have all learned to love Google analytics, but sometimes it's too slow.  If you need to know right away the impact of your campaign, you need to have real-time information, captured via dashboard.  I am a great believer of metrics.  You can find a lot of interesting patterns, and see things way before they will actually happen.  Complicated metrics presented in simple terms is an art.  Because at the end of the day, it's your investors and founders that have to see them and make important business decisions.  The more the metrics, the more visibility into the business.  However, most startups don't qualify to have metrics because you need to have traction before applying any real metrics rules. 

For mytweetmark, every time the mytweetmark link is clicked, the referer tracking will tell right away whether google, bing, facebook, twitter, mashable, techcrunch, any location's viralness is accessed and the impact of the campaign.  Lots of useful analytics can be built around this fashion.  It would also be very interesting from this traffic, mapping CTR to viral factor since every sign up or registration counts into the viral factor.  This is definitely something to be investigated and built into analytics in the future.

Here is a simple snapshot of mytweetmark internal dashboard screen fo referer tracking which is only accessed if you are an admin user.