Furthermore, the purveyors simply highlight that these seek to replicate (plus or minus 1 time or 2 times) the daily returns, and that they "do not seek to achieve their stated investment objective over a period of time greater than one day" ... despite presumably knowing full well people do not view mutual funds as one-day holds. Indeed, investors are sent a prospectus when they execute a trade, meaning that there is at least three days' price risk before they even get the prospectus, and that alone is enough to cause damage. In my mind, that is kind of like advertizing on the side of a cigarette box, "Not smoking these may have health benefits" instead of "Smoking these may be hazardous to your health." Both are true, but one does not fully disclose the risks of using the product. Maybe the cover of the prospectus should just say, "This product probably won't do what you think it'll do." As I said -- viscerally, these sound quite appealing. But their performance is more painful than a random walk. Nothing hurts more than being right but at the same time losing money -- I mean, Marc Faber and Harbinger must be horrified to see their names forever in print next to these gimmicks (at least the individual investor can remain anonymous). The sad thing is that anyone with a margin account can create a far, far more efficacious position to reflect bearish views. And for these professionals, there really is no plausible excuse but laziness. For those who argue, "Yes, but I've made so much money trading these" -- I'll tell you what: I will start an ETF based on an index linked to a random number generator. Whenever it is up and you are in the money, you can sell it and tell everyone in the chat room of your genius in knowing how to "ride the bumps." But for everyone else: If someone shows you a brand new deck of cards, on which the seal is not yet broken... Know what you own: Oberg mentions the ProShares Ultra Short funds. Other examples include the ProShares UltraShort QQQ (QID), ProShares UltraShort Oil & Gas (DUG) and the ProShares UltraShort Industrials (SIJ).The conversation on short ETFs continues on Stockpickr.