In 2017 many people have swapped Tulips for Bitcoins.
Think about it, the people who bought tulips on Feb 3 1637 could have made a fortune if they sold on Feb 4. But the ones who got in on the 4th lost everything on Feb 5th 1637. One day can break you in an irrational market run and today you won't even be left with a tulip to catch your tears.
The safe money to be made in Bitcoin has already come and gone. Visionary investors, early believers and the other who just got lucky were already in the Bitcoin market when it was under $1,000. Same was true for people who purchased tulips in 1634/35.
I can't predict if/when Bitcoin will crash. It could very well go to $25,000 in 2018 at this rate. But main street investors have to question what they are buying and with what risk profile. Do you even know your risk exposure in Bitcoin?