Occassionally, I hear the question asked, "Why do we even need denominations?" Although the primary focus of my blog is helping Christians work together across denominational lines, I do believe that denominations serve several good purposes. (DISCLAIMER: I'm making lots of generalizations here and these are non-research based opinions).
First, local churches need some kind of structure and accountability. Denominations provide local churches with an oversight, resources, and a kind of stability. And as I think about the history of the church, it seems like a de-centralized authority structure is necessary to provide checks and balances for the entire Body which we'll need until Jesus returns to earth. I think only Jesus could rule the entire Church.
Second, I think denominations help keep the whole church balanced theologically. When one part of the church emphasizes one aspect of the spiritual life too much, another part of the church brings emphasis back to forgotten aspects. It's so easy for us to go off on theological tangents that we need other believers to remind us of the other importants parts of the gospel (i.e., truth and grace, faith and works, God's part, our part, etc.).
Third, and this is similar to point 2, I think God uses different churches to bring good things to the rest of the body. Reformed churches have given all of us some solid theological thinking. Baptist churches remind us to keep winning souls. Pentecostal and Charismatic churches have given us fresh forms of worship and reminded us of how much we need the Holy Spirit. Anglican and Lutheran churches help us connect with our history (including emphasis on the practice of communion). Methodist churches have helped us keep our social conscience. Non-denominational churches have inspired us to stay on the cutting edge. My point is God has a lot of gifts for the whole body of Christ in these different churches.
Let me be clear that I realize there are tares in the wheat. Some people, some churches, and some entire denominations have left the faith. I'm just saying lets not burn the wheat because there are some tares in amongst it. Lets diligently stand for truth AND diligently connect with others who are doing the same even if they are in a different church. And let's appreciate what the different parts of the Body of Christ have to offer to the rest of us! Instead of focusing on what divides us, let's focus on how God has blessed other churches and what we can learn from each other.