Poloniex recently announced via twitter and its Team Circle Blog that as of September 25th it will be delisting 8 coins off of its exchange. The effected coins are BTCD, BTM (Bitmark), EMC2, GRC, NEOS, POT, VRC, XBC.
On Tuesday September 25th, at 12:00 ET, the following assets will be delisted from Poloniex: BTCD, BTM (Bitmark), EMC2, GRC, NEOS, POT, VRC, XBC.— Poloniex Exchange (@Poloniex) September 18, 2018
Poloniex is giving customers until the following month, October 25th to close out any trades and withdraw any funds from their wallets. After October 25th the assets will be completely unsupported.
Poloniex says that if any unforseen problems such as network conditions make withdrawal difficult it could extend the deadlines on a case by case basis.
The reason given for the delistings is to "improve the performance of the exchange and to better serve our customers."
Bitcoin Dark (BTCD) was in the news recently due to the fact that despite being an abandoned project, the price saw a mazzive 300% jump for no apparent reason. Rumors of insider pump and dump practices floated around social media. This could at least be part of the reason Poloniex is pulling this one asset, as they are one of the only exchanges still trading with it.