i find myself agreeing with zbird, joey, AND vortle.  Jewish identity IS all of those things.

 Two nights ago i had a wonderful conversation with my (orthodox, settler) rabbi about how to handle my brother's upcoming intermarriate to a non-jewish girl.  My brother is (barely) reform, same as my parents, but he actually does want a jewish wedding, and as the family 'expert' on judaism, he wants me to get him a tallit and ketubah.  I was feeling conflicted about this for a number of reasons, including halachic-- even as I might want to give my brother's wedding my blessing, to give it 'jewish' sanction as an orthodox jew, implying that I or that orthodox judaism approves of this, is problematic.

So I asked my rabbi, whose yeshiva is mostly baalei tchuva with non-religious or non-jewish or intermarried families, but whose ideology is that engagement with said families should always remain strong, unlike the haredi cut-yourself-off POV.  He actually told me I should do all that my brother wants and more, and if (as has been hinted at) his fiance is considering converting reform, I SHOULD encourage it even though Reform is so limited or 'wrong'.  His rationale, roughly:

at several points in Hebrew/Jewish history, identity was NOT so set in stone as modern halacha would have it.  It was largely patrilineal or 'either' through into 2nd temple times, according to pshat 'nach; and in Megillat Esther, a remarkable reference is made to people 'judaizing' ("mityahadim", i think) which implies linguistically that people were getting into judaism and identifying with us SHORT of some sort of elaborate, permanent conversion process.  Likewise in Roman times.  He then said that there is a tremendous blessing to people who openly make a public committment, in whatever form, to identify with am yisrael-- which certainly could include reform conversion and even Madonna. If these people want to call themselves Jewish, with all the dangers and downsides of that, we should welcome them with open arms.  In fact, we should recognize a category of "Jewish" which is NOT halachically Jewish, but which IS Jewish.  And for positive, not Nuremberg reasons (tho of course those are intertwined.

 Let's hear it for inclusive orthodoxy!  Am yisrael has far too many problems and enemies to waste time bickering amongst ourselves.  Anyone who wants to join our struggles, and our vulnerability, and our tikun in the world, is welcome: we need all the help we can get.