
This is a very sad story. Please remember everyone, that ANYTHING can be unsafe, no matter how hard we try. Whatever you personally decide to use in your cages, just remember the important thing to share here...
check their sleeping quarters, and toys as often as possible! 
Another note, to those that use knots... I didn't learn this until I was in my 40's and my son started cub scouts last year...
Left over right, Right over left...
That means that if you have two different color fleeces, and you are tying a double knot, you start with putting the "black" piece over the "white" piece on the first knot, then the "black" over the "white" again on the second knot. Don't just take my word for it, take 2 pieces of scrap and test it.
This type of knot is VERY hard to get un-done (although not impossible)... and because people don't do this when they tie their kid's shoes, that is EXACTLY why kids run around w/ their shoe-laces un-done all the time!
Hope this helps somebody out there, it surely helped me.
