Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
If I am not friends with a person on Facebook but can see their photos, can I "like" a photo?
Yes, it depends on their privacy settings, whether it is posted as "Public" or "Friends" or Some Customized list. It is just that if you see "Like" button, you can; if not, you cannot, and same goes for "Comment" and "Share" options.
Required, but never shown