Somebody says that derivatives are the worst thing in the (economic) world, but this is not an accurate assessment. Short-term debts, in general, are. Sometimes it seems rational to borrow at short maturity: it is less expensive and if you own valuable assets, you can hope to find always some lenders willingly to give you money. But this is not true.
This is the lesson from the Icelandic meltdown: the banks of that country did not use derivatives for speculative purposes, but they were heavily indebted on a short term on the wholesale market and they bought long-term assets. During the global crisis this system, which had been very profitable indeed for the whole