Mindings uses a Facebook "app" to import Facebook content and and "like" content on Facebook, this is the "Mindings" app which you authorise when you connect a Facebook account to Mindings.
Some users have their Facebook privacy settings configured to block access to their content from apps and so the content is not made available to Mindings. You'll need to contact the users in question and ask them to change their security settings if they want their content to be displayed on Mindings.
To do this they will need to; click on "Home" then "Privacy Settings", then click on the "Edit Settings" link next to the "Ads, Apps and Websites" section, and then click on the "Edit Settings" link next to the "How people bring your info to apps they use" section.
Once they've done this they will see a number of checkboxes which allow them to allow or disallow access to content from apps. If the "My status updates" and "My photos" are not ticked then they will need to tick them and click "Save Changes".