Visa has a market cap of 63 Billion.
EBay/Paypal has a market cap of 44 Billion.
Citigroup has a market cap of 142 Billion.
ETC...
So these industries could fall and all of their wealth would be redistributed. As a whole we would be wealthier.
What you guys don't understand is that bitcoin is NOT a replacement to banks, payment systems, etc.
Bitcoin is the equivalent of cash in the mail, with extra security features.
Think about it: you send a payment, it gets received (confirmed) some time later. (10, 20, 30 mins? still, it's delayed)
The mailmen are the other users generating blocks. They just can't steal.
If you send money to the wrong address, it gets lost. Like regular mail.
Once you send it, you can't get it back, unless you destroy the mailbox.
Would you base the world's economy on mail in the cash?
Personally, I would NOT...
This is the reason for stuff like Visa, Paypal, and others will surely survive.
Maybe one day they will adopt BTC as a currency, but no way they are going bankrupt just because of bitcoins!