The dollar is debt.
If you own a thousand dollars, you don't have a thousand dollar's worth of hard assets; a dollar isn't land, or gold, or coal or iron or water or food. If you own a thousand dollars, you have a thousand dollar's worth of other people's debt. Society owes you precisely one thousand dollars' worth of goods and services. It's an IOU you may cash at any time.
That's not necessarily a bad thing. On an individual level, sure, you might not want to deal with owing and owning debt. On a national scale, it works remarkably well; there are occasional corrections (2008 - if you're a company, don't buy assets you don't understand with only 5% as collateral where the 5% is based on a value you don't understand...) but it works pretty well. The strength of the world economy, in which almost every participating country's currency is debt just like the dollar, shows that it works quite well.
When you borrow money, thanks to fractional reserve banking, money basically... appears. This makes no sense, of course, until you realize again that dollars are debt, not property; the person with the dollars owns debt. The long-term effects of this I wouldn't hazard a guess, but in our lifetimes it will probably continue to work remarkably well. What that means, of course, is
When you borrow money, you create money; this money is then used to grow our economy.
As Greg said, "debt is encouraged to 'strengthen' our economy" and it's not wrong, and you shouldn't dismiss it out of hand because only stupid people owe debt instead of own debt. Regardless of your feelings on the subject, it works quite well. It's a system designed by people way, way smarter than us when it comes to economic policy, and it's participated in by all of us.