Marriage is a promise to do and not do certain things. Whether one realizes it or not, by marrying, one implicitly agrees to thousands of regulations and case law about property division, alimony, child custody, maintenance, "conjugal rights", bar on sexual intercourse with anyone else, and so on.
Marriage is not just a piece of paper, it is a legally enforceable contract with the modern state especially interested in enforcing it.
In most modern cultural settings, before one decides to commit to getting married, there is a period of courtship and "getting to know each other".
During that period, depending upon the cultural mores, there is a degree of physical intimacy up to and including sexual intercourse. Sexual compatibility is considered a major factor in deciding to get married to someone. In US and most parts of Europe, sex is a natural part of dating. It is becoming so in urban India as well.
The very purpose of dating and courtship is to determine whether a long-term bond is realizable or not. That long-term bond may eventuate into a state-sanctioned legal contract ("marriage") or it may remain informal (a "live-in").
In recent times in India, there is a growing tendency for grown, literate women (air-hostesses of Mumbai seem to be topping the charts here) to cry "rape" when a man they were involved with refuses to eventually sign the marriage contract. I call this a travesty.
The Indian High Courts are conflicted on this issue (the Bombay High Court clearly saying it is not rape), and the Supreme Court of India seems to side with the rape interpretation, while the case law is confusing.
Interpreting a "false promise of marriage" as "rape" is just another nail in the coffin of men's rights in India. Of course, the police is only too happy to register such cases and arrest the accused, as they are scared of the wrath of the feminist NGOs in case they refuse.
In my opinion, it is rape only if the raped person was coerced, intimidated or drugged. Inducing wistful daydreams, promises of everlasting love, and suchlike, is the very stuff that romance is made of. A romance not culminating in a contract is NOT a crime, it is a failure of compatibility, an emotional tragedy, a breaking of hearts, but it is NOT a crime.
If a woman alleges damages (loss of reputation, loss of virginity, pregnancy, etc.), then there are two questions to be asked:
1. Assuming the age of consent is not an issue, whether the sex was consensual.
2. Whether the sexual partners knew that the legal contract of marriage had not been signed yet. That is, there was no misconception that the marriage of some sort (say, at a temple) had already taken place.
If these two conditions are satisfied, then there is neither cheating, nor rape, nor can there be any question of exploitation. If the first condition is not satisfied, it is rape. If the second condition is not satisfied, then it is cheating.
If the woman is indeed wanting to protect her reputation and virginity, then let her withhold physical intimacy till the man signs the contract. If she is unwilling to get pregnant, let her use the pill or insist on safe sex.
If she is an adult, she should know the consequences of her actions and the law should not become a white-knight excusing her own culpability in the matter.
On the other hand, if she is not to be treated as an adult, then how can anyone even marry her? Then, she must be considered developmentally challenged, and treated at an appropriate facility. If she is an adult, then she, and the concerned police officials, must be tried for harassment and for making a false complaint.
A marriage is a promise. There cannot be a promise to make a promise. It is not a breach of contract to not sign a contract. It is as simple as that.