Today, Friday 17th of March 2017 we could witness severe order delays and freezes of the poloniex site, including the trading API. The image below shows an output of the XMR/BTC trading pair as displayed on cryptowat.ch, which represents the mess which traders had (and still have) to face today. Insiders are blaming the bots as well as a very high order volume for the issues, but the question remains why poloniex has not implemented a better scaling solution for their services.
The massive delays in the orders caused extreme spikes, especially for the XMR/BTC (Monero to Bitcoin) pair, which dropped from 0.02349496 to 0.01550000 at 2017-03-17 between 8:25 and 8:30 UTC. Following the dump, the prices were with massive delays cycling between 0.0175 and 0.0195. Currently the trading seems to be still very laggy, with a lot of orders not processing.
Similar issues have been reported at the ETH/BTC pair, with especially margin trading not being functional. ETH had a high of 0.04740000 BTC at 2017-03-17 07:15 UTC and 0.03131300 BTC low at 08:45 UTC.
Currently the markets seem to be recovering (at least for a small bit), the administrators of poloniex are reportedly "aware and working on the issues". Still there is no official statement from poloniex.
At the same time, Bitcoin/USDT is falling, which is also part of the instability problem at poloniex: 24h high was 1219.10 USDT yesterday (2017-03-16 18:30 UTC) and 24h low was 1052.00 USDT (2017-03-17 08:00 UTC).