The case of bitfinex is different, it has no correlation with the bitcoin movement. How to know if it is a bubble? That's a bit more complicated, usually the bubbles do not take long to explode and cause financial havoc, however bitcoin has managed to stay afloat and show that it does not have as many bubble features as it seems, everything is in the test of fire that would mean overcoming this year 2018 with all the denials from governments.