For long term holding, bitcoin never be dangerous.. Because bitcoin never gonna go down as far as i see.. But for day trading , you should be very careful with numbers.. Because even decimal points make big change in USD value. In that case btc is dangerous.. Thats the only place it becomes dangerous.. Otherwise bitcoin is very stable now a days.. Theres nothing to worry about it at all.. Even though crashes happened, all the times it came back much stronger.. Dont think twice to invest on btc..