Why through our weakness?

I was reading in II Corinthians this morning and a couple verses address the idea of weakness...
II Corinthians 13:3-4:
...since you are seeking for proof of the Christ who speaks in me, and who is not weak toward you, but mighty in you. For indeed He was crucified because of weakness, yet He lives because of the power of God. Fore we also are weak in Him, yet we will live with Him because of the power of God directed toward you.

What weakness was Christ crucified for?
I would say that sin is the weakness that Christ died for. That's the sunday school answer, but I think it rings true. Adam and Eve allowed their will and desire to take over when tempted to eat of the forbidden tree. Their initial sin is just a good example of the weakness of Man's will when it is outside of God. In verse 3 Paul says that Christ is mighty in us; and in verse 4 that because of the power of God, we will yet live with Him, that is Christ. When we rely on God's power, our weaknesses won't get in the way of living the life God intended for us.
In II Corinthians 12:9, God says "My grace is sufficient for you, for power is perfected in weakness." That's a popular verse that most people know and I think that together they show us one way God works in us to accomplish His will! Notice also that he says perfected, rather than just perfect.
To me that's an encouragement when I fail, knowing that God's work in my life to demonstrate His power is a work in progress and that's ok.

I'm sure most people know the phrase "you are only as strong as your weakest link." I think if God were to re-phrase it, He'd say "I am strongest through your weakest link."