Just to bring in another view, I Corinthians 11 is the passage that talks about taking communion "unworthily." A better translation is an unworthy manner. The manner which is being specifically spoken of in this passage is that certain people are being excluded from partaking because they are poor and working late, and the rich are getting drunk. As a result there's none left by the time the poor get there. It's interesting to me that Jesus seemingly made no effort to exclude Judas from the communion table.
I think the clear warning for the church is to not use communion as a way of defining who's in and out. Certainly there is room for church discipline and confronting sin, but using communion to do so brings judgment upon the leaders who do it.
That's very interesting to me, too. Then I thought that maybe the answer is in the very chapter you cited. 1 Cor. 11:28-30:
"28 A man ought to examine himself before he eats of the bread and drinks of the cup. 29 For anyone who eats and drinks without recognizing the body of the Lord eats and drinks judgment on himself. 30 That is why many among you are weak and sick, and a number of you have fallen asleep."
So, Judas partook and was unworthy. Soon thereafter, he was dead. Maybe it's the perfect example.