Irrespective what the course maintenance policy is I was told it was good practice to replace your divots from whence they came as a courtesy to following players. There is nothing more frustrating than to have a good shot come to a premature rest because someone did not consider others.
The Maintenance of the course is not within the remit of the golfer but courtesy and consideration under the etiquette rules is most certainly, so every effort should be made to reinstate the poor little sod back into his original home before he was so cruelly evicted. Leaving final repairs to those who know what they are doing.....
As a turfhead I would ask that you please replace you divots. As a player I request the same, I agree with MHM.
Reasons to replace: Affects the following players with the void or pelt, divots make areas appear unsightly, divots left out affect the turf it is lying on, affects mowing quality.
When I send out staff for divot repair duty the are asked to fill voids, remove dead or drying divots and fill, and clean up old divots.
Jon - It is never a waste of time to replace a bent divot, that said some turfgrasses (usually warm season grasses) will fill in a divot faster than a divot can reestablish.