While there is a problem with scalability in Bitcoin, the number of transactions required to create blocks that exceed the network speed is astronomically large. I ran some numbers to show this:
The USA handled 122.8 Billion non-cash transactions in 2012. I rounded this up to 150 Billion transactions.
In transactions per second: 4756 tx/s in 2013. Round up to 5000 tx/s
In transactions per block: 3000000
Thus, using the average transaction size of 0.2 Kilobytes, the block size would be 600000 Kb = 600 Mb.
Now, this is just the USA, with some inflated numbers, so the numbers worldwide are definitely higher, but not be too much.
Even with larger than 1 Gb blocks, the worldwide average network speed is 23.3 Mb/s, so I rounded down to 20 Mb/s.
The largest block size which could cause the scenario you outlined would be 12 Gb. Which could most definitely support all the worldwide non-cash transactions.
Of course, these numbers are averages, they could be higher, they could be lower. The internet speed depends on the location, the number of transactions depends on the time and place.
While the number transactions could pose a problem for block size and internet speeds, due to the astronomically large number of transactions to cause a problem, the core developers are not focusing on that yet. They will probably get around to addressing that issue, but they have other issues such as the size of the blockchain. This issue is currently being thought about and developers are attempting to resolve it. They will move onto other pressing issues first before coming to fixing the issue with download speeds.
If you have a solution to this issue you present, by all means, share it. Propose a BIP and submit it to the community and the core devs. It will eventually become implemented, and you will have just fixed a potentially big problem with Bitcoin for the future.
Ok that's 600 Mb/s for a average population of pool of 319 million, but we got 7 billion people, so on average that would be 22x bigger.
And let's ignore the fact that USA has more money to send / higher developed nation, i dont think with internet & bitcoin it would be that hard to get access to transactions. So we can safely include undeveloped regions like africa and south asia.
So in best case scenario we would face 13.2 Gb /block, if people would restrain themselves.
(Now i`m sure your statistic doesnt count HIGH FREQUENCY TRADING inside exchanges, nor other financial markets, only interbank transfers is it?)
But with bitcoin everything has to go through the blockchain, while you could have an exchange holding debt/ IOU /promissary notes, it will definitely increase it on the large run.
But what about malicious users?Suppose a malicious user would buy 1000 Bitcoin solely for the purpose of sabotaging the network, he then would send those 1000 Bitcoins in 1 satoshi pieces (even though he would have to wait 3-4 days)
or 1 satoshi with 10k satoshi fee, depending how it would be more efficient, back-and-forth between his addresses.
So he could generate 100,000,000,000 transactions in 1 round, then after 4 days another 100 billion.
Thus in 3 weeks he could generate 500 billion transactions ,that would make 1 block 2.4 gigabyte instantly.
In 2-3 months he could destroy Bitcoin literally.