It's good to have the advanced user options you mention, but they sound cumbersome and impractical. Hundreds of thousands of participants are being forced into a position of having th buy their freedom in order to make the spam-fight a little more convenient for a few admins, no?

Some questions:

• How does one get anonymous tokens? For existing users who need profile division, obviously anonymous tokens cannot draw from their existing account (it would defeat the purpose). It would be very cumbersome and also costly to deposit cash into a bitcoin ATM to seed this account, many of which require id anyway (a non-starter).
• Can the proof-of-work from the mining be transmitted entirely over Tor?
• The 5 dollar barrier-to-entry you mention is a bit excessive for contributors who are not participating for the money-centric aspects. That's a lot of money in some countries. 25 cents would be sufficient to make spam uninteresting. Why not lower the barrier-to-entry so users don't need to rent a server farm to get a libre account? (libre meaning freedom from privacy compromise)

The current model effectively encourages users to trade their privacy for time or money. That's also a problem because it victimizes the naïve -- those unaware of the compromise they're making, and those who won't discover they need privacy until it's too late and the information disclosure is used against them.