Interesting thread. Now to share my story.
I've been playing this game on and off for the past ten years. This game impacted me negatively during middle school and the first two years of high school. I spent too many hours playing, as a result my social life was very minimal.
Most of my time was used to make money via "flipping" and merchanting. When the grand exchange first came out my brother and I didn't really take advantage of it. However, we soon started to buy and sell items on the GE and found out relatively quickly that there was a "4-hour" rule, limits on buying, and the concept of "sniping." This got me hooked on "flipping." The skills I have gained from interacting with such a dynamic and volatile market place has actually helped with my studies in Business.
Runescape also got me into programming, I added a third major, Computer Science, halfway through my time at college and am loving it. Java and C++ are my life now.
This summer I wrote my own private script and ran it for 3 months before bots were nuked. Made some money. It was a lot of work but a very rewarding experience.
In the future I hope to write algorithms to trade stock or start my own online business.