Is it possible to have a multisite wide post type without duplicating the posts? That is a post type that is the same no matter what blog you are on?
Theoretical example: StackExchange has many sites (blogs) but wants their site-wide news post type, I'll call it
sitewide_news, to be the same on every blog. If they happen to be in blog id 4 and make a change or add a new post it will show up in 3 or 8 as if they made the change there. In other words only one database entry exists.