The interest which you can analyze via these charts is end-user interest. Bitcoin had and has the potential to become internet money, but for the simple minded end-user it seems unsecure (scams, gox,...). Additionally it is not needed at the moment because it's much more of a hassle to acquire bitcoins and buy stuff with it than just use your fiat. This is where I personally thought IT startups would fill the gap with clever ideas. The development to make it more user friendly didn't continue and the bitcoin believers where losing interest.

In the meantime companies and speculators are moving in and in my opinion their interest is not represented in that chart.  The bitcoin market is shifting towards being a financial market. And like in the stock market you can lose alot of money if you don't know what you're doing. Makes it less attractive for end-users using at payment option. I personally can't see how the monetary use and the financial market can happen in this small market at the same time.