The following is based on a conversation I had with Matt on Shabbat.
As many have pointed out before, the first ten chapters of B'midbar describe B'nei Yisrael's preparation for their journey to Canaan. After the "vaY'hi binsoa haAron" mini-book (see Shabbat 115a - 116b) the downward spiral of cheit begins culminating in forty years of wandering in the desert (see Rabbi Leibtag's shiur which deals nicely with this issue). Before the Torah completes its discussion of these preparation it records an a discussion that Moshe Rabbeinu had with Chovav/Yitro.
כט וַיֹּאמֶר מֹשֶׁה, לְחֹבָב בֶּן-רְעוּאֵל הַמִּדְיָנִי חֹתֵן מֹשֶׁה, נֹסְעִים אֲנַחְנוּ אֶל-הַמָּקוֹם אֲשֶׁר אָמַר יְהוָה, אֹתוֹ אֶתֵּן לָכֶם; לְכָה אִתָּנוּ וְהֵטַבְנוּ לָךְ, כִּי-יְהוָה דִּבֶּר-טוֹב עַל-יִשְׂרָאֵל. ל וַיֹּאמֶר אֵלָיו, לֹא אֵלֵךְ: כִּי אִם-אֶל-אַרְצִי וְאֶל-מוֹלַדְתִּי, אֵלֵךְ. לא וַיֹּאמֶר, אַל-נָא תַּעֲזֹב אֹתָנוּ: כִּי עַל-כֵּן יָדַעְתָּ, חֲנֹתֵנוּ בַּמִּדְבָּר, וְהָיִיתָ לָּנוּ, לְעֵינָיִם. לב וְהָיָה, כִּי-תֵלֵךְ עִמָּנוּ: וְהָיָה הַטּוֹב הַהוּא, אֲשֶׁר יֵיטִיב יְהוָה עִמָּנוּ--וְהֵטַבְנוּ לָךְ.
Moshe asks Chovav to join B'nei Yisrael in Canaan. Chovav resists his invitation and Moshe Rabbeinu persists. What place does this conversation have in the presentation of B'nei Yisrael's travel preparations?
This is not the only oddly placed dialogue between Chovav/Yitro and Moshe Rabbeinu. Before the Torah records the events at Har Sinai (Sh'mot 19) in Parashat Yitro the Torah presents Yitro's arrival and his discussion with Moshe Rabbeinu concerning the establishment of the best court system. As others have pointed out (see R' Yonatan Grossman's essay on Parashat B'haalot'cha for another approach) the placement of these Yitro/Chovav stories forms a chiastic structure:
YITRO -- HAR SINAI -- CHOVAV
B'nei Yisrael's entire encampment at Har Sinai is bookended by these two episodes. What is the purpose of this placement?
First I will try to explain the Yitro--Har Sinai connection. At Sinai B'nei Yisrael received the Divine Laws of the Torah. This law system was like no other because its source was not the mind of man. The God-givenness of the Torah could lead to a fundamental misconception: the wisdom of man has no place in the Torah. The story of Yitro is the corrective. The Torah can not function without man's wisdom - could B'nei Yisrael be governed by the Torah with only Moshe Rabbeinu to judge them? Of course, man's wisdom must be checked by God's wisdom - Yitro gave the proviso that his advise should only be followed if God commands it (Sh'mot 18:23), "וְצִוְּךָ אֱלֹהִים". However, here the Torah gives credit to Yitro and not God's command (v. 24), "וַיִּשְׁמַע מֹשֶׁה, לְקוֹל חֹתְנוֹ; וַיַּעַשׂ, כֹּל אֲשֶׁר אָמָר". The story of Yitro protects us from getting swept away with the Divinity of the Torah and, so to speak, lose our minds.
What is the Har Sinai--Chovav connection? There is another fallacy B'nei Yisrael had to guard themselves from as they prepared to enter Canaan: that the Torah is exclusively for them. In other words, is the Torah and the tremendous goods (both physical and spiritual) that it has to offer only for B'nei Yisrael? Loyalty to one's tribe is certainly virtuous but tribalism can not be allowed to degenerate into xenophobic exclusivism. The treasures of the Torah are not for B'nei Yisrael alone. What better demonstration of this truth than Moshe Rabbeinu's invitation to Chovav to join B'nei Yisrael and share in the good that God is to bestow upon them. Here too Moshe Rabbeinu expresses the peoples indebtedness to Chovav - he will be their eyes!
The bookending of the Yitro/Chovav stories seems to underscore the proper role B'nei Yisrael are to take amongst the nations. Not as cloistered priests living isolated from the rest of humanity but as ministering priests inspiring humanity to enjoy the true goods the Torah has to offer, להסתופף תחת כנפי השכינה. However, our connectedness to the other nations is not a one way street. Our ears can not be closed to the general wisdom of the world lest: נָבֹל תִּבֹּל--גַּם-אַתָּה, גַּם-הָעָם הַזֶּה אֲשֶׁר עִמָּךְ: כִּי-כָבֵד מִמְּךָ הַדָּבָר, לֹא-תוּכַל עֲשֹׂהוּ לְבַדֶּךָ.