Remove the tinfoil hats
totally agree... it would be unlikely for hashfast to be mining with customer hardware when customers have got pitchforks and torches outside the castle. there is little to no chance that this is a hashfast address. it just much too open... its the number one contributor on eligius. why would they be operating a 'secret mine' so openly. much too blatant (thus extremely unlikely to be them) !
although i do wonder what happens during their burn in tests... they must mine somewhere. i wonder, even if the burnin was just a few hours for each miner... i wonder how many bitcoins could be earned doing legitimate burnins on 550 batch 1 baby jets.
If HF is already mining, they could be part of the reason for the growth of the Unknown-part on blockchain.info's Hashrate Distribution last 5-7 days:
https://blockchain.info/pools?timespan=4days
https://blockchain.info/pools?timespan=48hrs
https://blockchain.info/pools?timespan=24hrs