I actually wondered with regards to TTD's 64's pool (I use btw). I am not saying this is happening at all, unlikely but think of the scenario

We mine to a pool like TTD. in the background TTD is receiving back all addresses and private keys. They could potentially have a bloom filter with a list of all addresses with a balance. checking every key against that. Basically making a cracking pool. I know the odds are still astronomical but it could be done. but would it ever be profitable? searching for more keys than just a single puzzle tx?

I am not condoning this btw, I would never steal, it's just a theory.