What the doctrine of verbal inspiration particularly safeguards is an implication of this basic fact. Because revelation was given in a specific form, that form is not incidental or accidental, and cannot be changed, ignored or somehow minimised. Just as you could not be a committed Yahwist and yet dispense with certain ceremonies of the law; just as you could not be a disciple of Jesus and yet ignore a few things he said ("get behind me Satan"!); just as you could not be a primitive Christian and yet disparage the authority of the apostles; so you cannot be a Christian today and not take every word, phrase, concept, image - in short, every jot and tittle - of Scripture with absolute, earnest seriousness.
God revealed himself in Christ. God commissioned the apostles as his witnesses. God oversaw the preaching, teaching and writing of the apostles such that their witness is also his witness by the Holy Spirit. And that witness is now collected for us in Holy Scripture, which we must take as it comes, recognising our inability to establish even one thing about God without it.
The way the doctrine of verbal inspiration has traditionally been stated and used, and particularly the place it has been given at the very doorway of evangelical theology, can (and I think should) be subjected to critique. But we must be absolutely certain that the critique of this doctrine is not driven by a desire to wriggle out of the fact that Scripture comes to us in a concrete, solid form - a form with edges, as it were - which we must take seriously and must consider ourselves bound to. Otherwise, the slide into idolatry has already begun. We begin by assuming that the form in which God's revelation comes is secondary - just packaging. That implicitly permits us to engage in the task of discerning what is 'secondary' and can be discarded and what is 'the real thing'. And that, of course, allows our preferences to override God's revelation. May he keep us from it.
Now, there's much that could be said in critique of Barth's doctrine of inspiration, but in defence of the master I must point out that he definitely believes in verbal inspiration as I have just stated it, and I'd like to leave off with a quote from him. (You can find it on page 533 of CD 1.2)
We can sum up all that must be said on this point in the statement that faith in the inspiration of the Bible stands or falls by whether the concrete life of the Church and of the members of the Church is a life really dominated by the exegesis of the Bible. If the Biblical text in its literalness as a text does not force itself upon us, or if we have the freedom word by word to shake ourselves loose from it, what meaning is there in our protestation that the Bible is inspired and the Word of God? To say "Lord, Lord" is not enough. What matters is to do the will of God if we are to know His grace and truth - for that is the inspiration of the Bible.