This post is presumably part of the patio11 campaign to boost Fog Creek's SEO and conversion rates by publishing "content you can't get anywhere else". Looking good!
That's what I thought, but FogCreek and Joel Spolsky probably has billions of in bound links from Joel's writing. Surely they wouldn't need to attract in links?
1. The fact that Joel's blog is on a separate domain means that Fog Creek doesn't reap all the SEO benefits that it could have from links to his writing.
2. Having people visiting the same website where the software is actually sold gets them one step closer to purchasing.
3. There's the "top of mind" marketing effect of constantly having Fog Creek's blog posts on the front page of HN and other tech news aggregators.
You should really read the thread and post I linked above, Patrick goes over exactly what they're getting out of the new arrangement.
Also, Joel's stopped blogging for the most part so Joel on Software links might not maintain their current worth forever.
I'm not sure it's possible to have "enough" inbound links, assuming you are able to make a profit on each new customer. Given a certain level of profitable business and submaximal SEO, effort aimed at improving SEO and conversions will be the highest bang for your buck.
http://news.ycombinator.com/item?id=2588431