Source: http://www.qldbridge.com/ 
THESE are simple hands but BBO experts went badly wrong on each of them so there must be a lesson for some readers.
Why don’t they bid?
North would no doubt justify his initial pass citing the adverse vulnerability. This is yet another of the great misconceptions of bridge. The time to bid is at the first opportunity. Assume partner is sane and you will not go beyond the safety of the 2-level without a big fit or game values. For mine the hand is an opener, either 1 or 2. 1 works much better here. There was, but shouldn’t have been, an opportunity to double 3, that was missed too. And whatever dissuaded South from bidding? Was it the vulnerability too? No accolades to West for his series of meaningless bids. South led the K.
I was declarer and saw that the contract appeared to depend upon the A being onside with one remote extra chance; North holding QJ10. With any lesser holding he can unblock them. I eliminated spades, making my line of play obvious. North’s Q should have dematerialized under dummy’s A but being as sound asleep in the play as in the bidding he held on to it. When it popped on the second round my only problem was to guess the original holding. When I guessed right, leaving him on lead, the contract made.
It is evident that 4 is cold for NS as is 3NT for EW. 4 is more likely to be reached after a 1H opening. Had North bid his hearts, or doubled 3, the defence against 5 becomes sleep proof.
Why don’t they shut up?
What an awful system that requires you to double on the North cards. Spare me please. If playing this style, forcing free-bids, I prefer pass. On the actual auction I see no justification for the 4 bid. Game chances are infinitesimal and they are at the 3-level. Just what outcome are you looking for? Shut up and defend! The opening lead was the 2 to the J, K and 8.
My dummy was greeted with, “QJxx hearts partner ?????” The message I understood was that I had a clear double of 3H to save him from himself.
West returned the 10 to the J and K. Declarer ruffed the heart return and missed the chance to keep his under- tricks to one by continuing with the J pinning the 9.
Readers will note that should I double 3, the play of the hand becomes double dummy. As is so often the case when you know there is trump length under you, the best play is a big one, this time the 9 from dummy. Just try to defeat 3 after that beginning. I did my part, I shut up. Without the help of a double from me, 3 will probably fail. Partner’s 4 was a clear failure to do so, as was his comment. A great maxim, “If you want to defend, pass.”
Why don’t they think?
It is against my principles to pre-empt with a bad suit, but eight of them?
North might seriously contemplate 5, given that South has bid 4 vulnerable missing AQ he will surely hold eight or nine of them, and surely that K is a trick? 5 will make if declarer takes a not unreasonable view in clubs. The time to bid it, of course, is directly. You may even get to defend a five-level contract.
North’s second time to think was when my club lead went to the A and K. Is there a chance in the world that that K is not singleton? Looking at the heart suit in dummy a thinking North would see that as remote as it may be the only chance to defeat this contract is in diamonds. If East holds the A, you will be writing down minus 680 regardless of his diamond holding. On the wooden club continuation, declarer ruffed and put me in with my A. I switched to a diamond but partner could only sit back helpless while declarer played five rounds of hearts getting rid of two diamonds.