In reply to Bradley Allen.

On reflection I would need to add that, if the end-user is happy to put up with it, its not 'harmful', and its in a product he/she has not paid for, then there really is no need to go to the extent of making a closed system and inventing rules and enforcing dictates about advertising/upsells is there.

The more greedy the author becomes and the more aggressive the interruptions, the will be the take up by new users.

The market will out in the end.