The common terminology is "rolling blackouts"

and they most certainly do happen.

With only so much bandwidth available, and millions of listings, there are times when none of your listings are visible to everyone (the days when regular customers ask why you have nothing in your store X-( ), days where some of your listings are visible to everyone, and days when all of your listings are visible to everyone.... I am absolutely sure of this.

I also think (but only have anecdotal proof) that there are times when only certain categories are visible, or when only certain states can see them. (this makes sense to me when suddenly every sale is to WA, or Qld, etc)