2 things. . .
First, as this is only the second time I've ever heard of a Fiskars hatchet failing in any way I'm not going to worry about mine suddenly breaking. As has been said it's probably just a defective piece that slipped past quality control. No reason to panic and get rid of a wonderful tool.
Second, Morablades, you have the opportunity to satisfy my curiosity. I've wondered for a long time exactly what the head of the Fiskars hatchet looks like under that plastic. If you opt to just move on to something new and not send in your broken hatchet for replacement could you PLEASE destroy it a little further and take some pics of a de-handled Fiskars for me/us? If it's shaped the way I think it is then it would probably be very feasible to attach a new handle similar to the ones on the stone axes that puukkoman posted pics of. it wouldn't function as a splitter any more, but should still be usable for chopping. If you want to go ahead and send it in for replacement I'll understand, but then I'll eventually have to go and spend 20 bucks on another Fiskars hatchet to destroy just to satisfy my curiosity.