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If it later turns out that the keypair generated by the third party is defective, your money is forever lost. You could just as easily create the initial pair yourself as validate it. In any event, it's not really two factor since both factors are the same (something you have). – David Schwartz – 2012-08-02T22:28:57.247

@DavidSchwartz - a probabilistic verification process: you order 100 key pairs, and test 99 of them. If they're ok, it's very unlikely that the hundredth one (which you'll use for real) is defective. – ripper234 – 2012-08-03T05:08:36.497

Also, you can generate the two keys yourself on N different devices (Android + Windows + Mac + Linux), and test each part separately. The odds that all four systems have Trojans are vastly reduced. https://en.bitcoin.it/wiki/User:Casascius/Base58Check-encoded_objects_proposal#Proposed_specification_for_a_multi-part_key_using_EC_multiplication

It's not that hard to make sure your key generation systems aren't trojaned. The hard part is securing your key storage systems. This just seems to make more problems than it solves. Though I suppose maybe somebody has a problem that it solves. – David Schwartz – 2012-08-03T10:00:16.867