Check my logic. I don't see the point.

As I understand the problem-to-solve is that if someone reveals your identity for any transaction then any other spends from the same public key are associated with your identity and any spends (inputs) from other public keys to the same transactions as the identified public key are with high-likelihood associated with your identity.

The CoinJoin solution is dual pronged in that if a greater percentage of blockchain transactions are inputs from multiple parties, then the high-likelihood case is reduced in likelihood for all users of the blockchain that don't use CoinJoin. The second prong is the mixing of parties for a transaction using CoinJoin protects the identity of the public keys for the parties spending using CoinJoin.

Note the first prong is an improvement even when someone reveals your identity for all the input public keys of a transaction, because you may use one of those public keys later with other uncompromised public keys in other transactions that were not revealed.

However, CoinJoin is unnecessary if no one ever knows your identity.

If you must provide your identity, then why are you using Bitcoin and not your credit card, cash, money order, paypal, etc?

I suppose there are rare cases where you want to give your identity to someone trusted but not the identity of the merchant to your bank. But that hardly seems like a compelling use case to justify such convoluted systems as proposed for CoinJoin. Credit card numbers can be stolen but in the relatively rare event, most of the time your issuer will remove any unauthorized charges. If identity theft is your concern, then again why are you providing your identity.

And against the NSA and the government, plausible deniability is not a defense (btw jim is James A Donald, first person ever publicly recorded as interacting with Satoshi). So if they know your IP then they can compel you to unmix all the mixing stages.

Thus, I view zerocoin and CoinJoin as a lower priority than a high-latency Chaum mix-net (or dc-net), which we don't have available today.

If you are littering your identity all over the web, then nothing is going to help you.