Am using Pro Sites to give access to the MarketPress plugin. When Pro Site expires, the plugin deactivates properly on the site, but the products remain displayed in the Global Products listing on the main site. This creates a disconnect to visitors browsing the global marketplace when they click through and find nothing.
This, of course, is a result of the global products being a separate database record than the Pro Site. As part of the upcoming integration for MarketPress and Pro Sites, when a Pro site expires, the products should be automatically removed from the global marketplace. Perhaps a new column in the main site's mp_products table to show a status as active/inactive/expired or, something that causes the entry to be deleted when the subsite expires and then causes the products on that site to be recreated in that table when Pro Site is active again.
Right now, I'm having to either manually extend the sites to maintain continuity (not a good solution because I want the site owners to pay) or manually track down and delete the products of expired subsites in the database.