I think you should never reject a calling. If you're telling the truth to your bishop then hes going to give you a calling your worthy for. Heavenly Father gives people callings because they are whats best for them. For example President Monson could have easily rejected his calling as a bishop, but because he accepted he was able to progress and further become prophet.
I don't think people should feel guilty when they reject a calling [Yes] know what I am saying? If they cannot fulfill it for whatever reason we don't know about then they can't its not the end of the world and people shouldnt make them feel guilty.
I believe that we should take it home and pray about it. Seek confirmation and follow the inspiration. I have heard of G.A. Who's wife turn it down. He stated my wife has already 7 callings. The bishop said 7? Nobody has 7 callings in the ward. The G.A. Cited 5 kids and two more areas of responsibilities. The point he made was: the most important things we do are within the 4 walls of our house. And at the moment that was all the sister could handle. So we should not automatically accept a call and then try to fit everything else in. Seek the Lord. You might not think you can fit it in but if the call is truly inspired He will help you. If not, turn it down. No harm done. We still believe in Agency.
Name: Nena
Comments: Sometimes the bishopric uses it as a "tool" for the "inactive" to help become more "active".
If one feels that the Bishop may not be aware of certain circumstance that might affect your ability to fulfill the calling, then, of course, you should make him aware of those circumstances, and then, if he still feels that it is the will of the Lord that you be called to that calling, you should consider carefully and prayerfully that the Lord may be the one that you are rejecting, and not the Bishop.
Is there a consequence from the Lord when we reject a calling? Is it necessary to have a calling to serve others? Sometimes due to many circumstances some members may not be able to accept a calling.