My Reddit Karma count tells a story that highlights some of the issues of Reddit's reward system.

The break down is roughly 160k link karma and 200k comment karma. The comment karma is indeed mostly original content, and took 5 years to gather. Meanwhile, the 160k link karma was reposts from other sites, and took roughly 12 days to acquire. Once the system is learned, gaming it for (meaningless) karma gains is easy. Of course the only real gains are realized by Reddit itself. And within that lies the issue.