Men are caretakers (qawwamuna) of women, because of that through which Allah has favored one over another, and because of what they spend of their property (Qur'an 4:34). 

They have no knowledge of it whatsoever: they but follow opinion, and opinion avails nothing in place of the Truth (Qur'an 53:28). 

This is more necessary today than ever, when so much Islamic thought abounds and so little of what in previous centuries of Islamic learning was called ilm or "knowledge". The good news reaches us that some academic celebrity or other has become a Muslim, only to be followed a few months later by the bad news: that he has written a new book about Islam. The knowledge of Islam, encompassing the entire ethical range of human experience, this world and the next, has never been considered attainable without learning it from those who have a working familiarity with it, the traditional ulama. It was once said to Imam Abu Hanifa, "In such and such a mosque there is a circle that discusses fiqh (lit. the "understanding of fine points of the religion")". He asked, "Do they have a master over them?" and they said no. He said, "They will never understand" (Ibn Muflih, al-Adab al-shariyya wa al-minah al-mariyya. 3 vols. Cairo n.d. Reprint. Cairo: Maktaba Ibn Taymiya, 1398/1978, 3.374). 

It is true that if such a celebrity confines himself to description of some particular Islamic phenomenon in ways he has been previously trained to, there is perhaps no harm in it. But when he tries an ethical analysis of what the Qur'an (or hadith) tells Muslims to do, he has passed into explaining the command of Allah, and in such a case, if he does not know the interpretive dimensions of that command--the aspects of Arabic, the figurative, the literal, the types of metaphor, the context in which various verses were revealed, which verses supersede others and which are superseded, the points on which there is scholarly consensus (ijma) and the points on which there is not, the tenets of faith of Ahl al-Sunna, and a great deal more--he will fail. 

Interpreting the word qawwamuna in the above verse is just such an ethical analysis, with human implications too tremendous to be left to amateurs. We will therefore turn to what some of the principle Imams of tafsir or Qur'anic exegesis have said about it. One of the earliest tafsirs in print is by Imam Ibn Jarir al-Tabari (d. 310/923), who says: 

Allah, majestic be His praise, means by Men are caretakers of women that they are in charge of their womenfolk, in disciplining and guidance, respecting the rights that they [women] owe to Allah and to them. Because of that by which Allah has favored one over another means because of that through which Allah has favored men over their wives, since men must give them their marriage payment (mahr) and spend of their wealth to support them, and save them their pains and effort: that is the favoring of Allah Most Blessed and Exalted of men over women, and is why they have become caretakers of them who have authority over them regarding those of their affairs that Allah has given them charge of ... (Jami al-bayan an tawil ay al-Qur'an. 30 vols. Cairo n.d. Reprint (30 vols. in 15). Beirut: Dar al-Fikr, 1405/1984, 5.57). 

In fact, although the hadith scholar Imam al-Baghawi (d. 510/1117) also mentions this event in his Maalim al-Tanzil, neither he nor al-Tabari can produce an acceptable chain of transmission of it back to the Prophet (Allah bless him and give him peace), so for religious purposes, it is not well-documented enough to rely on for the verses interpretation, and al-Tabari's first interpretation is sounder. 

But whatever the sabab al-nuzul or "original occasion of revelation" of the verse, the intended meaning is not confined to that alone. As the Yemeni shari'a scholar and judge Abdullah Mahfuz Baalawi says, "The interpretive principle established by the scholarly consensus (ijma) of specialists in methodological bases (usul) of Sacred Law is that the point of primary texts [of the Qur'an and sunna] lies in the generality of their lexical significance, not the specificity pf their historical context [emphasis mine] (al-Sunna wa al-bid'a. Kuwait: Matabi al-Wazzan, 1404/1984, 33). 

In light of this important principle, the exegetes we will now examine adduce the significance of this verses placement in the Qur'an (for the order is also divinely revealed), coming as it does after the provisions for Islamic estate division (irth) in surat al-Nisa. The Arabic grammarian and exegete Abu Hayyan al-Nahwi (d. 754/1353) says of the verse "Men are caretakers of women": 

Because Allah Most High has mentioned [in preceding verses] the matter of men and women acquiring their appointed share and their estate-division inheritance, He [here] apprises them that men are in charge of the interests of women. Caretakers (qawwamuna) is an intensive form [indicating something done much]. Because Allah has favored one over another means "because of Allah's favoring some men over others, this man having been given more sustenance (rizq) than that man, this man being better off than that one". And because they spend of their property means "upon women". The word ma [lit. what, translated above in the citation of al-Tabari as "because of that through which Allah has favored," and secondly, "because of what they spend"] is [rather] ma masdariyya or "the indefinite pronoun signifying a verbal noun" in both instances. [Thus meaning "because of Allah's favoring the one," and "because of their spending of their property,"] (Tafsir al-nahr al-madd min al-Bahr al-muhit. 2 vols. in 3. Beirut: Dar al-Janan and Mu'assasa al-Kutub al-Thaqafiyya, 1407/1987, 1.45758). 

Finally, the more fiqh-oriented exegesis of al-Kaya al-Harrasi notes that while Allah has mentioned men's support of women in verses such as the one in surat al-Tahrim "Let him who possesses plenty spend of his plenty; and let him whose provision is straitened spend of what Allah has given him" (Qur'an 65:7), in this verse [Men are caretakers (qawwamuna) of women], He mentions the necessary cause (`illa) for this support, so scholars have naturally inferred from the two verses taken together that whenever a husband is unable to support his wife, he is no longer her caretaker: she is not obliged to remain at home [should he request it] in any school of jurisprudence, and according to the school of al-Shafi'i (Allah be well pleased with him), she is entitled to have the marriage annulled. He is no longer a caretaker or entitled to oblige her to remain at home because he has vitiated the objective of protecting her by marriage, for the aim of marriage is her security (Ahkam al-Qur'an. 4 vols. Cairo n.d. Reprint (4 vols. in 2). Beirut: Dar al-Kutub al-Ilmiyya, 1405/1985, 2.449). 

In answer to your question then, our exegetes clarify how the meaning of qawwamuna or "caretakers" involves legal rights and obligations on the part of both men and women. It entails that women have the right to security, protection, and to be free from the thought of having to support themselves. Even if a woman has millions, she is entitled to be completely supported by her husband and can have her marriage annulled if he is unable to. And it entails that a man has charge of his wife's interests, supervision, and discipline. And Allah knows best.