Users are able to create their own trial organizations in Flowdock. This can cause issues if the user then creates a flow and invites users into that flow since the trial org will expire in 30 days.
Is there a way to prevent users from creating a trial organization?
There is no way to prevent users from creating their own organizations.
User accounts are loosely affiliated with an organization. Since a user can be associated with multiple organization, there is no way for a single organization to create a policy that prevents a user's capabilities in another organization, including the ability to create a new organization.