“Messianic Judaism” is a catch-all for a vague and general idea that attracts millions: the Jewish cultural context of the Bible virtually ignored in Christendom for millennia. Millions of Christians of all stripes and persuasions, from the Catholic and Orthodox Christian world to the Protestant, Evangelical, and Charismatic world are hungry to know more about Jesus the Rabbi. ... But many “Messianic Jewish” groups are simply Christians confused about who they are, who Israel is, and what God is doing in these times with his people Israel.
He goes on to list a few of the extremes, such as the "Two House" movement (the idea that all European Christians are probably descended from the 10 lost tribes, and therefore ought to be living kosher), those who view the traditional church as a pagan counterfit of what was meant to be the church, those who believe all believers need to be Torah observant, and more. Anyone who, like me, has tried to learn about Messianic Judaism by trying to read through the trail of web pages and chat room strings, will recognise them all.
At least I'm glad to have come across Derek's blog some time ago. Here's his own take on it, which I fully support:
Messianic Judaism at the core is about Jews and Gentiles who come alongside these Jews to be part of God’s work in the remnant of Israel. We believe that God is calling Jewish people to faith in Messiah within Judaism. ... Messianic Judaism is not an alternative to the Church. Messianic Judaism is a movement within Judaism formed by God and expressing in word and deed a Jewish faith in Yeshua.
Anyway, have a read yourself...