I just put up a post about this same situation as well. I really wanted to take advantage of the price spread and it doesn't make sense to me that there are so many trades going on over at Poloniex. Why would someone pay $1.70 for Steem Dollars when it is being sold for $1.42 on Bittrex? It doesn't make sense. Someone has to be getting through or something. I refuse to believe those are just the trades for the coins that were sitting on there from earlier.
https://steemit.com/steem/@brianphobos/help-me-figure-something-out-steemians-so-we-can-all-get-rich