While you can certainly earn a lot of money as an SEO on your own, you can absolutely make a good living as an SEO in the corporate world. Plus, as an in-house SEO guy, you don't have to worry about dealing with clients, billing, and other bullshit. You don't have to worry about finding offers and dealing with legit third parties. You don't have to put any of your own $ at risk.
This of course coming from a guy that does SEO/internet marketing for an agency. It's fun working on all different types of campaigns, clients, and industries. I also like the guaranteed paycheck and being able to work with other smart, fun people in an amazing office downtown. I get paid pretty well, too. And nobody is stopping me from doing my own thing on the side...
To have the opportunity to work with someone like markus would be reason enough for someone to try this!