Update: The associatedcompanyid contact property will become read-only on April 26th

When the HubSpot CRM originally launched, contacts could only be associated with a single company. This association was done using the associatedcompanyid, since only a single association from a contact to a single company was supported. Since then, we've added new objects, such as tickets and products, and also added support for parent and child companies. These new objects, and the new relationships between these objects, have required several updates to the systems that are used to manage those associations.