The main difference between popular "bubbles" like estate bubble, DOTCOMs or tulips in 17th century and Bitcoin, is that in all the aforementioned cases was a moment of overall realising that some asset really worthless. Bitcoin are not confirmed by gold, but it has a value. Even if btc is overpriced, there won't be a large one day drop to $3000, like "expert" said a few days ago. Price may go down, but it will go slow. Thats why its important to track your coins properly. I use https://coinsharbor.com to see all the my coins price movements. Very useful site.