The stated purpose of shunning and snubbing is to create pain and induce the victim to return to the control of the Book Publishing Corporation in order to end the pain. The real reason is to protect the members from information and facts known by the outcasts, i.e. information control.
I'd have to disagree. Shunning was around long before we had such easy access to information. 30 years ago, if somebody got DFed, it wasn't like they could start poking around and find anti-JW info and a support group of ex-JWs. Before the internet, finding this stuff wasn't easy. Bookstores didn't often carry books about it. Even now, I never see books like COC at Barnes and Noble. Back then, you were on your own. I'd have to agree that nowdays, it also helps to serve that purpose. But I don't think that's what it was dreamt up to do.
Is shunning biblical? I'm not saying the JW version is, but the concept does seem to appear in the Bible. It seems to be saying stay away from bad people who have no will to change. Not the JW version where you can be DFed for things like smoking. But it does seem like a good general rule. Stay away from people who are hurtful or have no concern for others. Seemed like it was more of a warning to believers about others rather than a way to punish believers who make mistakes now and then.
As for whether the JW version works? I always saw it as cruel. I knew two people, one a close friend, John, the other more of an aquaintance, Mike. Both were DFed at different times for unrelated things. Both put up an effort to get reinstated, but were never cut a break. Mike's car broke down in the middle of winter and he walked the rest of the way to the hall, but was rebuked for being late and it was counted against him. John was rejected by his sister and was deeply hurt by the loss of friends and the coldness of the elders. During this time, they kept in contact with each other and I kept in contact with John. So, they weren't completely cut off. I'd see Mike every now and then and at least give him a nod or smile and say hi. Talking to him was risky for me. At one point, he took a cleaning job at the company I worked for, so in privacy, we got to talk more. He really appreciated the fact that my brother and I cared enough to acknowledge him and it meant more to him than the coldness of the congregation - especially since we weren't really friends.
By making it so hard to return, both of them gave up, each for their own reasons. So in these cases, the shunning actually drove them away. If the elders were a little more leniant and gave them some more slack and reinstated them sooner, they may have returned and may be good JWs to this day. In this cong, people often had to pay their dues for a year or two. In other states, I heard of reinstatements in as little as 6 weeks to 2 months.
To add insult to injury, at some point, the WBTS determined that people who were never baptised could not be DFed. John, growing up "in the truth", but never getting baptised fit into this category. Suddenly his sister welcomed him and reestablished contact. The only thing that changed about John was how an organization categorized him. One day he's off limits, the next he's OK. So, basically, he was wrongly shunned by so-called "God's Organization". According to the JW view, apparently God saw fit to mess up John's life and deeply hurt him because he wasn't ready to reveal this technicality about non-baptised ones to his people yet.