Membership of the Xhire mailing list is very carefully controlled: It is not possible to join via an automated system.
The original list was made up of known contacts from the VMI Cross Hire list. Subsequently anyone wishing to join has to be from a recognised broadcast hire company, or provide references from a current member. In this way, someone who rents a couple of cameras can also join, alongside larger companies.
The integrity of the list is checked periodically, and purged of nonexistent addresses.
More than 200 people receive Xhire mailings, and it is always possible that there will be a rogue employee amongst the recipients who passes on information, but even if this happens, the effect would merely be to deter them from trying to defraud member companies, because they will know that the community has been alerted.