I wonder if there's not some sort of content-estuary (for lack of a better term) effect that Twitter causes?
Twitter is a massive content stream with all sorts of sources of content flowing through it, and when you're using Twitter, you can curate the sources of the content using lists and who you follow so that you get more of the content you want.
Over time, however, I have found myself interested in only a few content providers - to the point that I frequent their websites directly rather than Twitter itself. So I have paddled my boat off of the Mississippi that is Twitter and found a more comfortable, manageable home in a few smaller, content streams.
Quantcast will only see web traffic and create estimates from their panel + live cookie data. A lot of Twitter's usage is via mobile or API which will not be reported in these numbers.
Twitter is a massive content stream with all sorts of sources of content flowing through it, and when you're using Twitter, you can curate the sources of the content using lists and who you follow so that you get more of the content you want.
Over time, however, I have found myself interested in only a few content providers - to the point that I frequent their websites directly rather than Twitter itself. So I have paddled my boat off of the Mississippi that is Twitter and found a more comfortable, manageable home in a few smaller, content streams.