Clearly you've laid out a convincing argument. I'm sure you have mining pools contacting you already asking to be involved in this effort. We have to hurry. The longer we wait the more time the thieves will have to hide their trail and disperse the stolen bit coins throughout the economy. Please get me the required signed statement as soon as possible.
Do you have any suggestions on how much "taint" is sufficient to authorize a "lock"? Will the output have to be proven to be 100% entirely from the MtGox theft? Maybe anything more than 90% tainted should be locked? Really since we are using 50% of the hashing power to enforce the rules, perhaps we should consider anything more than 50% tainted should be locked. Come to think of it, given the "ethical imperative" and the "massive fraud or theft", I suppose the best thing to do is consider anything more than 0.1% tainted to be lockable. It should be acceptable to temporarily lock valid bitcoins to protect the community from assisting the thief.
Since anyone with any tainted bitcoins at all is a potential thief, it might be a good idea to lock all their bitcoins, and not just the tainted outputs. Therefore, if any address has even a single output that is at least 0.1% tainted, we should probably lock all the unspent outputs that are currently associated with that address.
Furthermore, we shouldn't be letting a thief spend any other bitcoins that they control (since we may need to seize these in the future to compensate the victims). Therefore, any address that ever had any of its outputs used as inputs in a transaction with an address that is being locked should also be locked.
We need to get a list of addresses from MtGox as soon as possible. In the meantime, please present any reasonably reliable list that you've found.
Barring that, we need to quickly establish the set of specific criteria that an address will have to meet to be locked.
Again, time is our enemy on this. Please contact some of the many miners that obviously would be interested in this. We need to pressure at least one mining pool to go along with it if you don't already have buy-in from the operator of the mining pool.
If there aren't any major mining pool operators that understand the importance of this, perhaps you can organize a boycott? If you can get enough miners to agree to withhold their hashing equipment from the pool until the pool succumbs to the community pressure, then we may be able to change their minds.
Anxiously waiting for a pool operator to agree to the plan...