I think that only a few major players would survive even if there were profit. Because, the data can only be sold once. Once someone know that this account is associated with one person they would not have to buy that information again. They can just grab the transaction from blockchain.info or by running a full node themselves.
And more importantly, would you really trust a bunch full node owners that would sell your data in a heartbeat?
Wouldn't the system be more secure, if a bunch of people who know nothing about programming run full nodes? For that to happen, you need to give people incentive to do so.
The average person is already not running a full node because of e-wallets and electrum.
Thank you for running the full nodes.
If the systems pay people for running full nodes, we can destroy the miners monopoly on the supply of bitcoins. This improve circulation of bitcoins, which in turn reduces scarcity that is the main reason for today's poverty.
A question:
If all the top miners collaborate to hoard the bitcoins they mine, where would the bitcoins come from for everybody else?
How would people with no bitcoins obtain a bitcoin? Without subjecting themselves to the control of whoever has a bitcoin.