If you trade a 3x leveraged fund with 4x intraday margin on a retail account then that's adds up to 12x margin - which approximates margin on index futures.
A better idea would have been to create an 3x ETF based on the S&P 500 - that would've attracted huge volume.
The 3x leverage only...
Google Trailer Fee.
http://www.investopedia.com/terms/t/trailerfee.asp
Its used by mutual and hedge funds. Usually its a fraction of 1% paid quarterly or yearly.
The CDS market may be huge in terms of notional value but it is largely illiquid. I doubt there are daytraders or market makers in the CDS market (I hope I'm wrong).
All it takes is one bad weekend headline to blow up a huge CDS seller (AIG style).
CME members have put up $101 billion...
If the Fed and Treasury are pushing hard for the CME clearinghouse then it will probably happen soon. That is bad news considering the CME Group is now the CME, CBOT, and NYMEX - if they miscalculate the risk no futures broker will be safe.