It would be impossible to do this as its anonymous when creating a bitcoin client. The only way of doing this would be to have a built in survey in all clients and that would be impossible.
Demographics would be impossible but a run through the block chain would reveal all wallets and the amount in them. That would give you a wallet distribution. I'm not sure the value since it will just make me feel poor.
No it would not.
Address =/= Wallet.
A wallet consists of one or more addresses. My wallet has >3,700 addresses used. Please look through the blockchain and find all 3,700 addresses.
You could make a distribution of addresses but since an individual can have any number of addresses it would be next to useless.
A distribution of wallet balances is impossible.