My opinion on the matter is:
1. You can’t reasonably force someone who shared an item privately to post it on the blog. If anyone would be forced into that, they could either permanently move or permanently decide not share anything anymore.
2. You can’t expect people that received an item privately to post it against the wishes of the sharer. The consequences for that can be easily understood by anyone.
3. 1 Week for sharing an item after a private share, as stated in the rules, is way too short of a time-frame IMO. My guess is that someone wouldn’t mind seeing “their” item on the blog as much after a considerably longer time, such as 1 month (a. to give PAs time to make some earning and not destroy his/her business, and b. so that the private sharer would mind less).