There's also allegations about exchanges like Bitfinex where the owners/management trade on their own exchanges [0]. With insight on order book and people's stop prices there's an obvious conflict of interest there, as one can easily go stop hunting and manipulate prices. It's an unregulated market, and exchanges want to keep it that way (like how Binance's moving operations to Malta)

[0]: https://medium.com/@bitfinexed/wash-trading-bitcoin-part-ii-...