Can entities as users exist without being tied to nodes Can entities as users exist without being tied to nodes, I'm starting a site that I don't want a lot of overhead and it will have a lot of users and they will be contacting each other often.
In D7 Users are an Entity type, they are their own Entity type. A Node is another entity type with various bundles such as Page, Article, etc.

Taxonomy is another example of an Entity.

An Entity does not necessarily mean a "Node" in drupal 7.

See this introduction to Drupal 7 Entities on drupal.org