Thank you for sharing this @stan, I had read about this a few days ago and I feel very positive about Circle buying Poloniex - they have a pretty solid track record and have overcome some issues in the past, so I am confident that they will do well.
I know some people who work at Circle, and honestly I was worried about them jumping on the bandwagon and launching an ICO out of thin air; not a good long term strategy. Seeing that they are buying an exchange first (maybe they won't ICO, but I presume they will do something similar to Binance if they do) is a huge positive in my opinion.
The thing is with Circle is that they will have a huge use case regarding the tokenomic properties of their tokens, and as well as that they should have relatively large volumes trading immediately due to the popularity of Poloniex.
I agree that there are positives and negatives regarding the current price of STEEM because of the acquisition, but at the same time if Circle introduced a FIAT gateway this could drive the price up.