A resource is rivalrous if one person’s use reduces or eliminates another person’s use, e.g. car parking. Common goods are rivalrous.
A resource is non-rivalrous if one’s use makes no difference to use by others, e.g. broadcast TV. Public goods are non-rivalrous.
The more people share an anti-rivalrous good, the more each person gets out of it, e.g. use of a natural language, adoption of HTTP, perhaps social networking.
Interpersonal data may be anti-rivalrous if we can address privacy concerns.