Perhaps you are looking for something more sinister here, but from that graph it seems to me that the likeliest explanation of the ballooning swaps on Finex is simply that they have gained a lot of users since December. I don't know for how long they have existed but I didn't actually try trading there until last winter, as part of me moving away from MtGox, and I suspect that may be true for a lot of other users as well. I think you would find that everything from Kraken to Huobi gained a lot of users during that time period.

I disagree that USD swaps balloons more than BTC swaps in general in your graph. If you cut out June the trend is not nearly as pronounced. In fact, both swap pairs follow an upwards trajectory with two major exceptions: people were in general very bearish in February (omg! look at those slopes!), and people are very bullish in June. You can also see the formation of a bullish trend in January which later falls apart spectacularly, and I think we all know why that was.

These things are quite easy to spot in retrospect of course. The question is what it means for us right now, and the heavy slant towards USD swaps right now probably means that a lot of people are long on Bitcoin at the moment. That may lead to a spectacular dip if/when they get squeezed, but it could just as easily lead to a rallly. Everything depends on how the price develops during the following weeks/month. Exciting times ahead for all you fellow adrenaline junkies .