Once there was a Chinese farmer who worked his poor farm together with his son and their horse. When the horse ran off one day, neighbors came to say, How unfortunate for you! The farmer replied, Maybe yes, maybe no.
When the horse returned, followed by a herd of wild horses, the neighbors gathered around and exclaimed, What good luck for you! The farmer stayed calm and replied, Maybe yes, maybe no.
While trying to tame one of wild horses, the farmers son fell, and broke his leg. He had to rest up and couldnt help with the farm chores. How sad for you, the neighbors cried. Maybe yes, maybe no, said the farmer.
Shortly thereafter, a neighboring army threatened the farmers village. All the young men in the village were drafted to fight the invaders. Many died. But the farmers son had been left out of the fighting because of his broken leg. People said to the farmer, What a good thing your son couldnt fight! Maybe yes, maybe no, was all the farmer said.
I've heard that one before...but TIL why everyone thinks Taoists (and Kabbalic Semites) are such smug assholes.

Would greater value invite greater incentive to steal said value?
Does ETH's magnitude-higher volume suggest a greater amount of crypto held in hot wallets?
idk, maybe it could turn out that some ETH hack too soon causes Poloniex to fold under excessive liability (unlikely, I know, but could the possibility exist?)
Also, could sophisticated finance that is more likely accompanying ETH trading leak into XMR trading and usurp control of the market, skimming outsider traders?
I have no idea.
Edit: Here's a maybe more tangibly plausible scenario. Could sudden increase in ETH traders increase overhead costs like account verification, support, etc. to cause an increase in fees to pay for overhead (if overhead costs from a flux of new accounts is greater than what current volumes and the fee schedule can provide)?
Another: could increase in workload from ETH overstress Tristan too much to the point of detriment? I suggest this because I just talked to him yesterday and he mentioned he's been insanely busy. I wished him that everyday is a day closer to an autonomous Poloniex.