"...Probably the only shared characteristic would be that these are things you can’t really get unmotivated people to grasp, but if someone is motivated, they’ll find their way in somehow. And enjoy it, after all, it is supposed to be fun, isn’t it?"
from the interview with Roger Bivand by Miguel Eduardo Gil Biraud
Links:
[1] http://spatial-analyst.net/book/quotes/author/Roger Bivand, Norwegian School of Economics and Business Administration