Darren Rowse started blogging in 2002. Yet he was earning a very good income entirely from blogging by 2005.
Now, there are squillions of Darren Rowse wannabes. The market is completely saturated with "make money from your blog" type blogs. I doubt very many of them make a decent income. There's just not that much left to go around!
Of course, Rowse continues to do very well out of Problogger. He's still on top of that niche, and will remain there.
He could easily have been satisfied with his achievements and simply stopped striving. But what's interesting is that he didn't. He's now heavily into Twitter and he has an excellent site full of tips on how to use that social networking site effectively.
You can see why he's done so well for himself. He's worked hard, kept his eyes wide open and kept looking beyond the horizon to see what the next big thing would be.
That's definitely a good lesson for anyone trying to succeed online - or in any medium for that matter.