A short sale is not the same thing as a foreclosure. Unlike during a foreclosure, the homeowner is very much involved in a short sale. In fact, homeowners who decide to short sell are usually trying to avoid foreclosure by working out a deal with the bank. When you buy a foreclosed home, you sometimes have to worry about evicting the previous owners, and that's not a problem with a completed short sale.
For the seller, a short sale doesn't impact your credit in the same way that a foreclosure would. It's still a black mark on your credit score, but it doesn't damage your credit for as long. With a short sale, you can take out another home loan in as little as two years, whereas a foreclosure stays on your credit report for up to 10 years.