Niccolò Machiavelli, in his seminal 'The Prince', CHAPTER XVII : "Concerning Cruelty And Clemency, And Whether It Is Better To Be Loved Than Feared" writes:
Upon this a question arises: whether it be better to be loved than feared or feared than loved? It may be answered that one should wish to be both, but, because it is difficult to unite them in one person, is much safer to be feared than loved, when, of the two, either must be dispensed with. Because this is to be asserted in general of men, that they are ungrateful, fickle, false, cowardly, covetous, and as long as you succeed they are yours entirely; they will offer you their blood, property, life and children, as is said above, when the need is far distant; but when it approaches they turn against you. And that prince who, relying entirely on their promises, has neglected other precautions, is ruined; because friendships that are obtained by payments, and not by greatness or nobility of mind, may indeed be earned, but they are not secured, and in time of need cannot be relied upon; and men have less scruple in offending one who is beloved than one who is feared, for love is preserved by the link of obligation which, owing to the baseness of men, is broken at every opportunity for their advantage; but fear preserves you by a dread of punishment which never fails.
[Sidenote: the book did not actually have a title when it was written by Machiavelli]
In Economics, we call this as a Matching Market. Love belongs to the Matching Market whereas Fear is not. In a Matching Market, there is a willingness to sell a service or good by a Seller, and a willingness on the side of the Buyer to buy the service or the good at the said terms. The transaction does not happen otherwise. Organ Trades, and others are examples of such Matching Markets.
Other examples of matching markets include Jobs, Organ Transplants, Room Allocations, Marriages, Loans etc.
In Love, this commonality of needs or wants is necessary. But Fear is a one way street. Fear is inculcated by the Perpetrator onto the victim. It can so happen that Victim need not fear the actions by the Perpetrator, and hence this equation is purely based on the magnitude of the actions by the Perpetrator. Fear is also a perception and is determinant on the Perceiver; what can be otherwise 'normal' actions by a do-er can cause fear in the minds of the Receiver/Victim.
But both Love and Fear, suffer from a serious handicap. Handicap of Impermanence; that is, the feeling of Love and Fear is temporary and can either fade or strengthen with the passage of time. You might Love something today, and something else tomorrow. Fear is similar; what you are afraid of today, need not make you cringe in fear the day after. Impermanence is a beautiful concept and is the underlying theory that causes more trouble in the hearts of Humans. We abhor Impermanence as we do not understand it. We are never taught of Impermanence in our education and hence most of Humanity(especially the Western World) fears Death.
In Bhaja Govindam, this is stated beautifully:
ma kuru dhana, jana , youvana garvam;Do not be proud of your wealth, relationships or youth. Time can snatch them away from you in no time.
harathi nimeshat kalat sarvam