Past bubble happened because people wired millions and millions on exchanges and you were clearly able to see it, among other things.
If price is about to go in a bubble you will be able to tell.
This time around it looks like nobody gives a flying fuck tho. At least for now.
$14-15M in bids currently on bistamp, bitfinex, btc-e, okcoin, huobi, btcchina, okcoin and coinbase ("$75M from NSYE!!!11!") combined, and still relentlessly going down.
3600 coins mined a day (almost $1M a day at current prices) and still 2 years of that shit.
Marketcap at $3.5-4 billion.