Answer
Mike van Rossum
07-Feb-2012 05:10:43
Here at Twitter Counter we track over 21 million Twitter accounts, as you can imagine this requires a lot of resources. To keep everything to a minimum we only track 'normal' account once a day (or sometimes a little less), if we miss a couple of days of data we try to calculate it as accurate as possible. Premium accounts will get tracked a couple of times a day, so they are a lot more accurate.