I did some searching but couldn't find anything about this specifically, but does anyone know what all can fire obs xp? I'll fill in what I know:

Looking at mobs: Yes
Considering mobs: ?
Killing mobs: ?
Looking at room desc objects: Yes
Looking at items you can hold: ?
Identifying/loring items: ?
Looking at room exits: ?
Anything else?

And obviously there are level restrictions for all of this (i.e. looking at a mob at level 5 might give you obs xp while looking at the same mob at 50 won't).