Of course everyone has the ability to track down the path of the coins and then possibly confront the perpetrator and request them to return the coins.
A while ago I decided to track down the 'allinvain' stolen coins and see where they ended up. It turned out that by mid February they were distributed to over 100,000 different addresses, including 8 of my own addresses. I'm guessing somebody did a very good job of laundering them. Either that, or this is just the natural way that bitcoins are passed around.
http://bitcoin.stackexchange.com/a/2900/659 is where I posted my findings.
Great analysis. A good example of why we can't blacklist coins.