Basically what happens is the following statement:
You have an element that pops the tribal hut. Can be units or culture borders.
When the tribal is accessed, it rolls a dice over different results. If the popping element doesn't allow the rolled result, like experience over a settler (popping element), the roll is cancelled and the dice roll starts again and it goes for 10 times max.
After 10 dice rolls in a row without a compatible result, the dice roll is stopped and the hut returns not only nothing but also no message (while CivIII returned "the tribe is deserted" I think).
All you to consider are:
Settler/Worker can't receive experiences
Healing doesn't happen to units with more than 1/3 of the full health bar
Culture border doesn't trigger experience.
Huts from a certain distance of the capital (and only the capital and I think it is 8 tiles away) are barb free.
Checking "No barbs" option will make huts free from barbs, this dice rolls for barbs don't happen.
Techs are not allowed without the first city settled
There are perhaps other possibilities, but my memory decay is doing its job gradually.
Now you basically know all about huts (perhaps to know furthermore that huts are separated mnimally by three tiles between them; for better hut pathfinder...), turn them off unless you just want some casual emotional bursts.