I don't think it is. If I refer a job to a friend, I do so knowing that particular friend can handle the job. Different jobs I'd refer to different people. Whenever I refer a job, I'm putting my name on the line in recommending that person. If they fail, the customer loses confidence in me as well.
What if you were only referring the job to your private network, of say 5-10 other freelancers who you trusted? Not the public network.
I just hire said freelancers as subcontractors, pay them, and deliver the work directly to my client. Simpler for the client, subcontractor gets easy work without worrying about client negotiation.