can you imagine the volume of activity when there are even 5 or 10 million on here?

I have to wonder... if the Blockchain will contain all of the content of all those people, won't it become so large that no regular user will be able to participate in the blockchain?

Downloading the BitCoin Blockchain right now is already a big task with ~200GB or so. This could lead to a situation where only certain individuals or organizations could continue to actively participate in the Blockchain.

Am I missing something or is this a problem that needs to be tackled?