I don't know. I feel like I would be more critical when referring a stranger. If a friend asks me to refer them to a big company, I would likely do so regardless of how good I think they'll be. But if some stranger does, I have no reason to refer this person. So I'll check out what they're doing, maybe look at a side project they're working on or read their blog. And if I think they would be a good fit I would only then refer.
Most places I worked were so desperate for job applications, especially ones that they didn't have to pay a head hunter for, that they'd take pretty much any referral. It has always been hard finding remotely qualified interested candidates.