Provisioning EC2 GPU instances and the like and writing the grammars.
If someone has the incentive to break into your wallet, all you need is a phrase long enough to make physical violence a better alternative for the attacker, and you're set, no need to make the phrase any longer.
Around 0.6% of all Bitcoin are known to be lost, so with unknown losses it could be 1-2%(https://bitcointalk.org/index.php?topic=7253.120)
Excluding the Pirate scam, 2.9% have been stolen. These are still viable, some are tainted since the receiver address is known. (https://bitcointalk.org/index.php?topic=83794.0)
A virus which deletes wallets instead of trying to exfiltrate BTC seems much easier to implement and would be pretty devastating for the currency.
