Most web publishers measure where their traffic is coming from using an analytics package such as Google Analytics, Omniture or Core Metrics.
These were good packages in the pre social media world at helping figure out who was driving your traffic.
Today they’re wrong. Terribly wrong. And figuring out who is referring your traffic is a very important part of determining how you allocate your marketing budgets. It is almost certain that Twitter is driving much more of your referrals than you think.
Possibly up to 4x as much.