Ash helped me once, creating this plugin code: http://pastebin.com/Egzm8ZBS that displays the latest posts from Pro and Elite users on our site. Unfortunately, we have some troubles with it. It also shows the posts of former Pro blogs, which is very bad, as it only be a Premium feature to have posts shown on the mainsite.
If you look at the attached screenshot, i have marked a former Pro blog (level 2), which is now a free blog, but it still shows up. It has the blog ID 43 - if you want to check it out.
Can you help me out? It is happening to a lot (if not all) blogs.