Imagine all the money exchange and circulation of the world economy. 7 billion people. If hypothetically Bitcoin would be the "world currency" how much data (which is never deleted) would that generate per day? What data will amassed in 10 years?

I wonder how that will hard limit the system...? I have no clue about Bitcoin but a quick google search seems to imply that the global history of all transactions is locally saved in the client as "blk0001.dat". Already this database seems to be a few hundred Megabytes big?

So Bitcoin's scalability relies on a mixture of writing new software when it's needed ("The core BitCoin network can scale to very high transaction rates assuming a distributed version of the node software is built. This would not be very complicated.") and in future switching to a two-tiered structure with "supernodes" transmitting data between themselves at a rate of >1GB/s. While I suppose that it's good that someone is thinking about this, it does not inspire confidence in bitcoin's ability to scale - the fact that it's theoretically possibly to write software allowing it to scale is very different from someone going off, writing this software, and demonstrating that it does scale.

The supernode architecture is mentally straightforward and has been the solution used by a number of previous P2P networks - eDonkey, Gnutella, and Skype come to mind as using supernodes or variants thereof. If you want to seriously criticize Bitcoin, one ought to have more than FUD and 'you haven't proven the opposite!'