Windshield problems of the 2001 Subaru Outback

It's been rather cold here the past couple days (single digits, -20 wind chill). I was sitting in my 2001 Outback yesterday evening letting it warm up. I turned on the defroster, windshield wiper defroster included. After a few minutes, I actually watched the windshield crack from both ends of the defroster element! when I got home I checked it out further. The crack extends the full length of the defroster element on the windshield. There was no impact of any kind. As this is obviously unsafe, I am having to pay $300 for a windshield replacement. This appears to be an ongoing issue with the Subaru Outbacks. I feel that this is a defective component and a major safety risk. Though the glass may not blow in, the shatter while driving down the expressway at 65 mph would certainly cause a major accident.