One major flaw found in the Male from the Twenty-first Century is : he never says who he is when he calls you on the phone.

Over the years I have been in contact with exactly ONE guy who did. And I'm not sure he counts because he's been in a relationship for, god, I think I actually lost count, but over 6 years now I think.

The crazy thing is, when the Male from the Twenty-first Century calls, he knows who he is and he's very likely to ASSUME that you know who he is too. So while he's leaving a message or whatever, you're really just trying to figure out who the hell you're talking to so OF COURSE you're not going to be extra-friendly, your concentration is elsewhere.
And then you come accross rude.

So if the Male from the Twenty-first Century would just learn to say his name when he makes a phone call, it could spare the whole world a great deal of misunderstandings.