I disagree. While I don't think the action should be taken lightly there are instances in which confirmed scammers should be taken to task by anyone with the ability to do so. If it's possible to confirm that it's indeed Tom mining on that account I'd seize it and return the proceeds to those he stole from were it up to me.
...but then I'd delete Giga's BFL orders as well.
I don't disagree with the sentiment. I just think that if you have a business which is toddling along very nicely and where you're not attracting any undue attention then you need to make a risk/reward assessment before you decide to play vigilante.
The amount which would be available for return to Tom's customers would likely be very small but the pools would be with-holding those funds from Tom and redistributing them without any legal authority (your employer can't just give your wages to a creditor because they don't like the fact that you haven't paid your bills - they need legal authority in the form of a garnishee order to do it).
You also have the issue of how a pool is meant to validate claims. Without access to Dave's list of those who are still owed refunds, there is no way to verify that those who claim they are owed refunds by Tom are legitimate.
I have no issue with services black-balling known scammers and refusing to do business with them - it's just problematic to enforce given the large number of services which allow their customers to remain anonymous.
I wouldn't be at all surprised to learn that Tom is effectively "judgement-proof" and has no significant assets beyond whatever is sitting in his BTC wallets - and we really have no idea of how many wallets he has or their addresses. Unless he has BTC-related accounts which are tied to his real life identity, denying him access to those accounts through civil law means is going to be difficult (law enforcement has far more options in this respect).
I think it's wise to remember that at least one criminal complaint has been filed in respect of Tom's activities and more will likely follow. The scope of those investigations may well extend to his earnings from mining pools, so it's in the interest of pool operators to maintain "clean hands" at this point.