I have been getting this since I upgraded to 8.1 a few days ago. I assumed it was because I am based in UK (we are usually offered new tech last). However, now I see others from around world are getting it, I can see it is global.
Glad to see I'm not the only one getting this problem, although if this thread is any indicator of the level of outrage I'm slightly concerned. Hopefully us in the small percentage of people still getting this will be allowed to update soon. If Microsoft are feeling generous enough.