Speaking as a Catholic married to a (non-observant) Jew, I agree with your observation. My sister-in-law is a Messianic Jew (Jews for Jesus) married to a Baptist, my wife's best friend is a Jewish woman who married an Italian guy. Another friend is a Italian woman married to a Jewish guy.
Basicly, when you're a Jew in an ocean of Christians, it's much more likely that you'll marry a Christian than a Jew, unless you have an inflexible criterion to only date Jews.
With an intermarriage rate around 50% for Reform and Conservative Jews, I expect Reform and Conservative Judaism to pretty-much disappear from the US within another 3 generations
I'm a member of a reform synagogue, and the christian in an interfaith marriage. There are a lot of mixed marriages in the temple, and we are doing just fine, numerically speaking.
I get annoyed when I hear folks talk about jewish-christian marriages like its some sort of communicable disease. We are not destroying judaism...but we are changing it. Given the large number of christians in our temple, the community has had to alter its views on things...politically and culturally. I think its a healthy process that brings in more points of view, as opposed to a narrow, ethnocentric viewpoint that has dominated judaism for some time.