companies flagging 'tainted' addresses/transactions and track where the money goes and what addresses have had questionable or confirmed blacklisted coins.
That's not the approach I would take at all. I'm not talking about black listing coins or implementing some kind of ban system. I'm talking about determining if the origin of the coins being paid were genuinely mined or not. It wouldn't be designed to track beyond that.
However, none of these are widely used for several reasons, the biggest two of which being that first and foremost, money is money to most people, and they don't care of it was stolen at one point
If that were true it would mean that most people don't care if they are really supporting the Bitcoin network or not. I, for one, want to make honest long term investments. The dollar in my hand may or may have at some point in it's life been stolen from someone, and sure, it is not relevant to me if it was, but I would care if the person pays me with money they stole.
that it is generally considered to be against bitcoins nature
How is it against Bitcoin's nature?
I don't think you'll be able to do that. Ponzi owners can always use any new address and you can't block them all from all wallets etc.
Who said anything about blocking? I'm not suggesting anything so drastic. I don't think anyone should ever implement blocking.
It doesn't matter how many times you change your address. A given coin is tracked by the network from the point of it's minting. All I want to do is arm the users with the ability to see at a glance if the operation is legit or not. What they do with that information is still up to them.
This could be interesting. You could have it see if the Bitcoin a few transactions back is coming from a known address used by a pool. You could also see if the Bitcoin a few transactions back is coming from a coinbase transaction because that would prove that they are either solo mining or in their own pool.
I don't think I would even have to go that far. The issue with going back to a known pool is that there may be a pool that I don't know about and it could also introduce a problem where inclusion of such a list would sanction the contents of it. I think it would be far simpler to first look at the transaction, track the source of all the coin to it's different sources, and run a comparison.