Until earlier this year I worked for a company that, among other things, develops and operates power projects in southeast Asia. We were a stodgy company using, if you can believe it, 100% equity for these projects. That is, until the last one which came online in late 1997. You see, in 1994-1997 all the power players in SE Asia were trying to emulate the slick new kid on the block who was getting all the attention and signing some great big new power supply contracts. This slick new company was called Enron, and it was leveraging these projects to the hilt in order to maximize ROI and minimize Enron capital. So all the other companies followed suit, borrowing roughly 80% of the capital required for the power projects. Well, when the Asian crisis of 1998 hit and the bottom fell out of the Asian currencies, the bottom also fell out of the Asian power market (remember the Asian tiger economies...where has that term gone?). In Indonesia pretty much every one of these contracts was cancelled or suspended (I happened to be acting GM when we received the cancellation letter and the sh*t hit the fan), resulting in lengthy renegotiations and new, much lower pricing. The only players who made it through those renegotiations without going bankrupt were those who had resisted the temptation of high leverage (okay, those with lots of political clout made it also). We all know what happened to Enron.
The company I worked for had leveraged its last ($600M) project at about 40%, and we just barely squeaked by servicing debt during the 5-6 years of renegotiation.
Okay, the US and even foreign stock markets are not subject to the same risks as a foreign power market, but my point is that, like "the force," leverage has its dark side. It all seems swell when you look at how leverage helps you on the upside, but you had better be sure that you know what a 25% market correction (even a short-term one) will do to you in a leveraged position, and that you have the stomach and the wallet for it. If you do, and if you have...go for it. I do, and I haven't.