The case against bitcoin, stated concisely by the Economist:
"It seems that every day, Bitcoin seems to hit a new high. But the reported price can move up and down by $1,000 or so within a few hours. This might have made it a great investment for those who got in at the right price and are nimble enough to get out in time. But it doesn't make it a useful means of exchange. When the price is rising fast, those who use bitcoin will be reluctant to part with it; when the price falls, those who sell goods will be reluctant to accept it."