This post is an expanded version of an email conversation with the Fleischer Rebbe, which he has posted as a comment.
The topic is the old "Who is a Jew?" question. The question doesn't affect me personally, because all of my known ancestors (later than Lavan ha-Arami, anyway) have been Jewish, so I'm Jewish according to all opinions, and because I hold no position of religious authority, so it's not my place to adjudicate anyone else's Jewish status. However, I can still comment, as an interested observer, on the discourse surrounding the question.
In 1983, the Reform movement's Central Conference of American Rabbis passed a resolution stating "that the child of one Jewish parent is under the presumption of Jewish descent. This presumption of the Jewish status of the offspring of any mixed marriage is to be established through appropriate and timely public and formal acts of identification with the Jewish faith and people." This resolution is often confusingly referred to (including by the CCAR itself) as "patrilineal descent", creating the misleading impression that the Reform movement traces Jewish lineage only through the father, rather than only through the mother. In fact, as the resolution states clearly, the child of one Jewish parent is to be treated the same regardless of whether the Jewish parent is male or female. One of the justifications for this position is the Reform movement's commitment to egalitarianism.
I'm not going to argue the merits of this position. The CCAR already argues it convincingly if you accept their premises, or unconvincingly if you don't. So it goes.
I am instead going to respond to the frequent allegation that the CCAR's resolution has singlehandedly split the Jewish people, an allegation made by Orthodox leaders claiming a monopoly on authentic Judaism, or by Conservative leaders looking for a Sister Souljah moment (and thus declaring the recognition of equilineal descent to be one of their Unforgivable Curses). The allegation goes like this: the Reform movement recognizes as Jewish a set of people whom the Orthodox movements and the Conservative movement considers not to be Jewish, and therefore, down the line, all Reform Jews will be of questionable status and we won't be able to marry each other.
Let's examine the practical consequences of the policy.
(But first, two postulates. 1) Intermarriage is a fact of American Jewish life that will be unaffected by any rabbinic pronouncements. 2) To the extent that Jewish communities are anything worth being a part of, intermarried families will want to be a part of them.)
Suppose a Reform Jewish man (call him Moshe) marries a non-Jewish woman (call her Tzipporah). They have a child (call him Gershom). Gershom is raised with a fully Jewish identity. According to the Reform movement, Gershom is Jewish. According to the Orthodox world, Gershom is not Jewish.
Now suppose the CCAR had never passed its equilineal descent policy, but this family still wants to make sure that Gershom is recognized as Jewish within their community. They have two options: 1) Tzipporah can convert before Gershom is born, so that Gershom is born to a Jewish mother. 2) Gershom can convert. But the problem with both of these solutions is that the Orthodox world doesn't recognize non-Orthodox conversions. Therefore, if Tzipporah or Gershom converts.... According to the Reform movement, Gershom is Jewish. According to the Orthodox world, Gershom is not Jewish. Presto, nothing has changed!
Okay, you ask, then why doesn't Tzipporah or Gershom get a conversion that will be recognized by the Orthodox? Well, if it were only a matter of going to the mikvah (as many, though not all, Reform converts do anyway), and in Gershom's case, having berit milah lesheim geirut, then this would seem like a reasonable price to pay for kelal Yisrael. But a central part of the conversion process is kabbalat 'ol mitzvot, accepting the yoke of the commandments. This is understood in different ways by different movements, and in an Orthodox conversion, this requires accepting the Orthodox understanding of the mitzvot. Orthodox batei din require conversion candidates to take on an Orthodox lifestyle completely, including davening only at Orthodox synagogues and sending their children to Orthodox day schools. It is completely unreasonable to expect that the Reform movement will require its converts to take on an Orthodox lifestyle!
Therefore, let's look at the practical effects of the CCAR's policy: The Reform movement gets to put its money where its mouth is about egalitarianism, and many people are welcomed into Jewish communities who otherwise wouldn't be, and there is zero adverse effect on kelal Yisrael.
Suppose Gershom grows up and wants to marry an Orthodox or Conservative woman (or, perhaps after this December, a Conservative man). Then the answer is the same, regardless of whether Gershom's Reform community recognizes him as Jewish from birth or whether he converts under Reform auspices: Gershom can convert (or reconvert) through a beit din that his would-be spouse recognizes. If Gershom is unwilling to do this, and they can't arrive at an agreement on the matter, then they shouldn't be getting married. One can cross this bridge when one comes to it.