jon,
what dauer said. personally, as the resident beardy fundamentalist (apparently) i have Views on intermarriage, but the fact is that it is a fact of life, even more so now that jews are marrying later and (it appears to me) getting more and more fussy. and clearly it has been a greater or lesser fact of life for a very long time, so i can only conclude that being raped by cossack is less likely these days, but then so is the entire nation deciding to convert at once like the khazars (see the "kuzari") and we gave up actively proselytising with the rise of christianity, although apparently many historians believe that rather a lot of the roman empire and middle east was made up of jews after the first wave of hellenisation. plus, of course, it's way too hard to convert according to halakhah these days. on the other hand the rate of assimilation in non-orthodox denominations is horribly high, which means that kids first end up not being actively jewish and end up by not being halakhically jewish, although obviously in many cases not being halakhically jewish is not necessarily an indicator of not being actively jewish in a non-orthodox context and sustaining judaism in this environment. and, of course, the haredim have huge numbers of kids, more than anyone, which means the situation has its own dynamic anyway. and syncretism isn't the way forward, either. any mention of the word "chrismukkah" will result in me foaming at the mouth.
b'shalom
bananabrain