Not only polo but any other third party exchanging services are free to disappear on us at any moment, not even governments could help us if they run away with our money, despite all the warnings I don't know why people aren't taking them seriously maybe they're waiting for the inevitable to happen and then cry afterwards. prevention is the best cure.
you can trade on a platform with a new york bitlicence, but as far as i can tell there aren't any.
Circle has had a BitLicense since 2015, but they pivoted away from Bitcoin. I think you can still send BTC and possibly other cryptos using it, but I don't think you can buy/sell anymore.
Ripple was awarded the second BitLicense in 2016. I used the Ripple interface to trade various currencies back in 2013, but they seemed to have made a lot of changes to the platform since then, so I'm not sure how you use it to trade now.
Most notably, Coinbase was awarded the third BitLicense. I heard that others, like CryptoFacilities, are in the process of seeking approval, but that's it for now.
the pathetic thing about poloniex is that they fell apart with 40,000 online users. what would happen to all the exchanges we have now if there was a real bubble and there were 1 million people online all at once? that's still nothing in internet terms.
That goes for all of the exchanges. Even the most well-funded exchanges in the world, like Coinbase, are incredibly unreliable -- APIs constantly dropping off, mismatching trade engines, constant server/website downtime and unplanned maintenance. By the standards of the stock or forex markets, the infrastructure around BTC trading is pathetic.
Sadly, this is one of the reasons why BTC-e was as popular as it was. It had one of the most reliable APIs and trade engines in the business.