I noticed that in some of my games, characters won't offer their minor quests when they should do so--case in point, Amren's sword, or Carlotta, both in Whiterun. The Amren quest should have been offered as he has the argument with his wife and then doesn't mention it to me.

Found the same bug in Windhelm, where the smith failed to offer the quest for the sword and an Argonian at the docks didn't offer up the Tobjorn quest.

In all cases I had done unusual things, like do many dungeons before entering Whiterun for the first time, or entering Windhelm for the first time using the "back" entrance from the docks. Anyone noticed this kind of thing?

Those might be Radiant quests that are not guaranteed to occur or they could be dependent on your faction as well (I know that Amren's Family Sword will have 2 different quest givers based on your faction for example).

Interesting... thx