This inoccuous joke-question gives us deep insights into Jewish culture. Taking as our subject the type of Jew who would ask this question, i.e., one with a high sense of ethnic awareness, we can arrive at four aspects of Jewish life that this mirrors.
1. The Jews are a social aggregate with a strong sense of identity and cleary defined interests.
2. Their interests are not necessarily aligned with that of society as a whole.
This may seem controversial, but it's connected to the statement. For example, look at the joke above. Isn't it clear landing on the moon is a good thing? In this joke, it isn't necessarily a good thing: a clever Jew takes a skeptical attitude towards any achievement as what may be good for others is not necessarily so for him.
Before you accuse me of anti-semitism, the statement can be taken philosemitically. For instance, Durban. Is an anti-racism convention a good thing? Of course it is. Is it good for the Jews? No it isn't, if a group of NGO's go around the UN sponsored building selling copies of The Protocols of the Elders of Zion and chanting "Hamas, Hamas, all the Jews to the Gas!". Is the fact that the interests of Jews are not allied with society the fault of the Jews in this case or in the fault of the antisemites and the NGO's who passively allow antisemites to hijack the convention?
All ethnic minorities partake of this ambiguity. Sticking to the idea of a moonlanding outlined in the joke above, there is a famous Gil Scott-Heron song called Whitey on the Moon. Part of the lyrics are "I can't pay my doctor bill/but whitey's on the moon".
3. Things in the interest of Jews are not 100% clear and need to be clarified. This is implicit in the fact that we are here dealing with a question, not a statement. Why would the Jewish mother ask if a moon landing is good for the Jews or not? Because it isn't clear. Nothing is seen as good or bad until every possible angle has been hashed out, clarified. There is a Talmudic tale in which God "punishes" a good man by destroying the wall of his house, and "rewards" a wicked man by letting him find gold. Without going into details, by the end of the story the good man is wealthy and healthy and the rich man's son is dead, all because of the consequences of the previous two events. See, for example, the book of Job. Nothing, even the goodness or badness of a moon landing, is taken for granted. This is the kind of Jewish skepticism that led to Freud, Marx, Jesus, and the anti-globalism of Naomi Klein, as well as the proglobalism of Thomas Friedman. Almost anything can be good or bad. We need to ask, and examine the answers.
4. Anything can be a basis for Jewish reflection. The Jew, the great universal cosmopolitan, is affected by all events. This is the basis of the moon landing joke. A famous Dry Bones (an Israeli humor strip) once asked the question: The Biafra uprising in Nigeria. Good for the Jews or bad for the Jews. The answer? Bad for the Jews. Why? Anything bad for anyone anywhere is probably bad for the Jews.
This isn't as arrogant as it seems when you consider that the Saudi Foreign Minister recently blamed a bombing in Riyadh on "Zionist agents." The question: "Extremists blow up a police station in Riyadh, galvanizing Saudi opinion against terrorists. Is it good for the Jews because it means that the Saudi man in the street will no longer support Hamas? No, it's bad for the Jews because they all think that Zionists did it." (Here you have a modern event that includes all four points in it.)
Interestingly, "Is it good for the Jews" is used by the MOST insular Jews, i.e., Hasidim, as a proxy for the simple question - what are the implications? For example, in the brokerage I used to work in, the Hasidic trader might say to the boss "Intel quarterly earnings are out at 46 cents a share." The boss would answer, "Is it good for the Jews or bad for the Jews?" This question meant, did it bring the stock up or down, and are we long or short? Here the question lost all meaning as an ethnic identity issue, and is simply an arrogation of ethnic characteristics to the most impersonal activity imaginable: stock market speculation. On the other hand, the question still underscores ethnic bonds in the office, since it's the type of a question only a Jew would ask and only a Jew would understand.
In Israel, the question doesn't exist, mainly since Jews are in the majority and are more comfortable in their own skin as it were. After all, any ethnicity constantly asking if external events are good or bad for it, is an ethnicity at the very least concerned about their own security.