[Executor]

As someone who had over 400 clams in a single game, and pretty much concentrated every game on them until they were removed I have to say I agree with Calahan, one player could have much worse stats in the score graphs and still be the far superior nation.
However limiting them to say 20 max per game for example shouldn't have much of an impact. There are various magic site discounts that act in the same way, while they don't give you gems per say, you do sort of 'gain' gems when using them. A fine line is to be made here, I neither agree that gem gens should have been removed completely or let to stay, same applies to both hammers and SDR. Eliminating any one of them will just lead to new problems that will need balancing, eg. cost of items, thug usage, blood supremacy of certain nations...
So rather than eliminating them all completely a compromise should be made.
As for monitoring their usage, that is rather simple, once victory is achieved a player will submit random mid-late game turns as to confirm there was no cheating, and/or trowing away of items near the end.