Dear Dr Date,
What is with men? Seriously, it has been horror story after horror story with my last few relationships. It’s the same with several other women I know. And it is not that we jump into relationships too quickly or blindly pursue people we don’t know. We have been very discriminating. I’m sure women are not alone here, men also get dished a fair amount of bullshit … but of a different variety.
There is one example I’d like your advice on (man to woman dishing, so to speak). I began seeing someone I really felt I connected with. Things were going very well, and he kept expressing how happy he was to meet me. Then nothing. He just stopped calling and didn’t return any of my correspondence. At one point I wondered whether he had suffered physical harm as that was a logical explanation for his not contacting me. But now I suspect I have become victim to a terrible yet widespread disease, disappearing male Homo sapiens. Why do these men we carefully hand select put on the “sensitive and trustworthy” facade before either cracking under pressure, or worse, dramatically slipping into oblivion? Why do they kid themselves that a relationship is what they are after in the first place?
Please to all men recently involved: communicate with the woman in your life, no matter if the news is good or bad. People are not immune to apathy.
— Righteous Sister

In general terms, there is a certain point at which two people make a spoken/unspoken agreement to behave nicely and responsibly. If you meet someone on the street and you hit it off, neither of you is required to follow any rules of etiquette. In other words, if someone you just met doesn’t come through and call, it’s your problem.
This most definitely happens to men, too. I hate to dissect a relationship too finitely, but it may help here. Until you go out on a first date, the person you are interested in is merely a prospect. Once the first date has happened, there isn’t a big change. First dates allow the participants to learn about one another. The second date is crucial, but it still does not require the other person to behave nicely. Same goes for the third, fourth and fifth dates. Your dating relationship can go on and on like this unless you have a talk.
At some point, the two of you will discuss what is going on and what behavior is expected of the other person. In colloquial terms, you’re going steady. This is where you determine if seeing other people is allowed or not.
Once you’ve had the talk, then he is morally obliged to let you know when he’s dumping you and vice versa. Up until that point there are no rules.