There have been various reports here that ads do not show up for prolonged periods of time on SO-Kindles (for unknown reasons), then start reappearing again. Maybe you simply started using it during a period where no ads were pushed out. Downloading ads of course also requires internet connectivity, as does web browsing. Maybe you have simply always been offline before that.
... and given that the thread title reads "Default zoom and Special Offers", I assume that you know that you have a KSO (even if you didn't mention anything concerning that in your first post).
