add the reason "it's a CPU coin".
It was a mixture of the fact that you had to look for new miner releases daily and had to tune arcane parameters all the time the fact that you are basically competing with botnets and cpu server farms which are still more numerous than GPU farms and you have the reason why a cpu coin will have difficulties maintaining value.
Also, for parameter tuning, instead of collecting parameters for different CPUs somewhere (as is the case for GPUs in litecoin/bitcoin wikis, but probably took some time until those were available as well), it was every greedy man for himself. Mining primecoin was a lot more work than any other recent coin, while you were competing with botnets.
all botnets do is dump immediately, the same as ASIC miners do for bitcoin since their chips are worth their price in metal otherwise.
The poll option "The fact that Mtmlr's GPU Miner does not work" implies this.
Can you add :
"more sellers than buyers "
To the poll ?
That's what the question is about, though. Of course that is why it's gone down. But WHY are there more sellers than buyers? That is the question.