Exchanges come and go like any other sites in crypto. I don't trust them, but I use it, becouse currently it seems to be one of the best exchange. Who knows what will come tomorrow? I never keep bigger amount on any site for longer time.
Yes, you are right. We never should forget that all online-based businesses are permanently on risk of disappearing, being hacked or facing multiple problems sooner or later. It is true that poloniex has been working well these years but it does not guarantee anything in future years, so we only should invest or hold here the coins that we could afford to lose.
