Especially when a dragon attacks and kills some npcs. People should move in over time to replace some of the dead characters

It's because procreation doesn't exist in the TES universe.

Dragons kill NPCs? Christ, now I'm gonna have to look out for that when I start the MQ. Haven't started on the MQ yet, so this was kind of a spoiler to me

Its very funny though to see that an old lady wielding am iron dagger thinkIng she can take on an ancient dragon

I cannot see the funny part in that (okay, I do xD). Poor old woman. To help, or not to help. That is the question. But being the Dovahkin I probably will (if I ever see her).

Specifically it's the crazy one in riverwood who says in her old voice "A dragon! I saw a dragon!"

Wait, if you are killing dragons then doesn't that mean that you've started the main quest??

Haha, that would be the mother of Sven. Yeah, she's not quite right. Well, I gotta say, she's got guts for trying to take on a bloody dragon by herself ^^
Though, if it's her, I'm not so sure about the helping part... I don't like Sven.

Ack, I hate it when non-essential NPCs insist on pitting themselves against dragons. I don't need septuagenarians as backup, man! I kill dragons for fun! Trust me, old lady, I got this! Get back to your grandkids! Please!

They are?!

Not on my current char. And I only started the MQ on my first char, though I didn't take her very far until I found only faults in her. So I've had a few char, but they've never been more than lvl 20 something before I grow tired of them and make a new one.
I think I only got to about five or six dragons on my first char where I started the MQ, but I never saw a NPC attacked. So one can say that I don't really know anything about the dragons.

Well put!

In one game I had every non-essential npc in dawnstar incinerated by an irate ancient dragon.

No they are not, really.
After playing Oblivion I saw how much Skyrim is perfect.

I have yet to see a dragon attack any kind of settlement... It probably gets annoying after a while but I keep hearing about it and I want to see it happen!