Also, due to popular demand, all users can close threads that they started - therefore, if you have had your question answered, you can close it and no more replies will be accepted.
As quoted by John

Can we not have this facility?

The PRO's that I can think of

1) Avoid unnecessary conversation post the 'resolution'
2) Avoids 'Rebirth' of Old Threads

CONS

1) Hmmm... Still thinking...