I do not think bitfinex abuses their postion; but ANY user with access to TIMELY information on the market DOES abuse it heavily; the 2-5 second delay bitfinex has can cause me 2% losses on any market order trade. Because, by some MIRACLE, hundreds of other users decide to make the same market orders in the very same split of a second as I do. This Results in my orders many time given the worst pricing

But I do not think bitfinex employees are actively behind it. This is by design.

P.S. yes, the NYSE and such traders actively abuse it as well. The very same way. They can cut in line because they KNOW sooner and EXECUTE sooner. Especially because they are machines.