A 51% attack in those days would have made no sense. These were the days before exchanges or even an exchange rate. To trade you had to post on a forum or IRC a

A 51% attack in those days would have made no sense. These were the days before exchanges or even an exchange rate. To trade you had to post on a forum or IRC and wait around for an answer. If the network was attacked, it would have been announced on those same forums. To pull off an attack you'd have to set up a room full of 100 computers CPU mining, hope that nobody noticed the hashrate suddenly doubling, and maybe get a few pennies worth of BTC for your efforts. There was a much easier way to get bitcoin back then: Go to the bitcoin faucet and type in your address.