Might get slated for this, but I don't think Mark Karpeles is that bad of a person
For the records, neither do I. But an epic fail can easily do as much damage as an epic act of villainy.
Anyway, the absolute worst for Bitcoin are speculators trying to use it as a tool to make (even) more money. Greedy people with lots of money can do serious damage to any business, but Bitcoin, being a new and revolutionary form of money, is especially prone to financial attacks, either by people trying to kill it or by people trying to profit from it.
speculators dont exactly destroy bitcoin. if they speculate and cause a price rise, that equals profits for the community. if they speculate the price down, that causes a nice buy-in oppertunity for new community members.
bitcoin protocol has decades to centuries of life ahead, the price variance does not impact this. even if the price suddenly dropped to a penny, you are sure as hell find a million people trying to buy as much bitcoin as they can, bringing the price right back up.
i would however say FUD spreaders, that are purely trying to sway people away from purchasing at any price are more damaging then speculators who just play the prices for profit.
and as for silkroad. although i do not condone their illegal activities. it has actually provided world wide press news and advertising to get people to ask the question "what is bitcoin", to which after they research bitcoin, they find out bitcoin is great for legit investments and value transfer and silk road is just hyped propaganda. thus they learn to separate the two whilst getting into bitcoin