Quote from plyka:
I actually read a book on LTCM but i've almost forgotten all of it by now, lol. I don't believe they were in arbitrage, from memory they had a number of different strategies, some of them extremely complex. They were overly levereged, things turned for the worse, and there they went.
In pure arbitrage, there can only be counter-party risk. Unless a clearing house goes bankrupt, i'm not sure how they can lose. As an example, let's say that the SPX futures for whatever reason are trading at a slightly more expensive price than the actual stocks in the index. This can happen for whatever reason, and usually only for a very short amount of time (due to arbitrage). Someone shorts the futures and buys the stocks/index in proportion. If we assume that we have factored out other things like interest/dividends/carry/whatever when they make the trade and there was a descrepancy, then they have already locked in their profits. It's similar to buying the ES and then selling the ES, there is no more risk to you, you are flat. If you buy and then sell the ES, this doesn't add to the total notional value of derivatives because we'll assume that the open interest in the ES first increased by 1 and then fell by 1. However, if you buy the ES and sell the actual stocks/index, this adds to the total notional value despite their being no real difference.