all Fridges will always be accessible to only those in the group. if you aren't in the group you don't have access to it. we are already seeing users create Fridges for larger and more "open" groups like conferences, events, interest groups, etc... and the members are the ones that share the invite URLs to add members.

the main point here is that members of one group do NOT have any information or access about the others groups you are in unless you share it. the group members of a Fridge can decide how open or closed they want their group to be.

in the future an administrator can customize group settings to enable a group to be "listed" or "discoverable" allowing organizations or events that want to open to be open. it would definitely be transparent to the members and settings ONLY for that group with their other groups closed, private, and not listed...