"No one can have God as Father who does not have the Church as Mother". So argued Cyprian in the early third century. His words would not be accepted by large swaths of Protestantism today as a Roman Catholic perversion of true heart religion (never mind that in the third century there was no Roman Catholic church, just the catholic church - the bishop of Rome not nearly as important at this phase in the church life as other bishops from Carthage or Alexandria). Other Protestants would agree with Cyprian, but quickly retreat to the idea of the invisible church.
Honestly, neither of these solutions is satisfactory to me. I hope, over the course of the next year, to read, think, meditate and write more on the doctrine of the church. Roman Catholics often charge that Protestants, especially evangelicals, have no doctrine of the church. I tend to agree, at least when it comes to contemporary evangelicalism. I don't think that was true of the Reformers, nor do I think it's true of many confessional Protestants today - Lutherans, Anglicans, certain Presbyterians, Reformed Churches, etc.
Is the church really as important as Cyprian made it. Consider this passage from 1 Corinthians 5:1-4,
"It is actually reported that there is sexual immorality among you, and of a kind that is not tolerated even among pagans, for a man has his father's wife.  And you are arrogant! Ought you not rather to mourn? Let him who has done this be removed from among you.  For though absent in body, I am present in spirit; and as if present, I have already pronounced judgment on the one who did such a thing.  When you are assembled in the name of the Lord Jesus and my spirit is present, with the power of our Lord Jesus,  you are to deliver this man to Satan for the destruction of the flesh, so that his spirit may be saved in the day of the Lord."
There is so much here to unpack, but notice just one key truth - being cut off, excommunicated, from the church was being 'handed over to Satan'. It was the most severe form of church discipline - a last ditch effort to convince the immoral brother or sister of their need to repent.
Think about what this entails. To truly punish my kids, I don't bar them from eating their vegetables or cleaning their room. Those aren't activities they deem important, valuable, or enjoyable. If I want to get at them, I bar them from the Wii, from TV, from sports activities, etc. Then I've taken away something that will hurt in the hopes that they will understand the gravity of their errant behavior/attitude. When the apostle Paul tells the Corinthians to bar the immoral brother from the fellowship, he is encouraging them to bar him from something that is incredibly good, valuable, essential - all in the hopes that this shock will awaken them to the gravity of the situation.
Why doesn't church discipline work well today? Lots of reasons. First and foremost, we have a pathetic view of the church! We have this "God-me-and-my-Bible" approach to piety that utterly disregards the role of the visible church. To be banned from church; honestly, not many would consider that a horrible fate. In fact, many have been 'self excommunicated' - choosing fellowship through the TV or the internet, or church on the golf course.
Only with a high view of the church as a mediator of divine grace does Paul's method of discipline make sense. In the church is sustenance for the Christian life: grace in the sacraments, the Word preached. Outside the visible church is the realm where Satan holds power - it is enemy territory. Facing it without the support of Mother Church is scary indeed.