I haven't been to Las Vegas in a year or so, but it was fairly safe then and it couldn't be as bad as Barcelona, Spain.
In Barcelona my wife and I got off a tour bus and watched a local man walk off with a ladies purse. It took two people to grab the man as he looked at them and finally let go of the purse.
Las Vegas may be slightly worse now than it was a year ago because of the depression they're going through, but it's always good to be on guard in any big city you visit.
As soon as I get a chance to visit Vegas, I'm going. There may be a rise in crime, but I'm sure there's also a rise in security too.