Edie, I absolutely agree with all the others: of course you can do the backstitch for quilting! This stitch was used about 600 years ago for the Tristan Quilt, made in Sicily - one of the oldest surviving examples of handquilted items.
If you are interested, look here:
http://www.illuminatedspaces.com/his.../qsource11.htm
So when you use this method you keep a tradition alive!