The grey area is massive. Take using photos. What if I run ads or have affiliate links on my blog? What if I'm a US not-for-profit that has $10s of millions in revenue? What if I'm giving a presentation at an industry event that I'm not being directly paid for but it's essentially part of my job?

I could go on but I guarantee that if you surveyed the readers of this site many people would answer those questions differently.

Effectively, if a lawyer were making the call of whether a particular use was OK, they'd tell you just not to use it because no use that you'd be asking a lawyer about is clearly OK.

> What if I run ads or have affiliate links on my blog?

FWIW, in Germany that would indeed make it a commercial endeavor.

It gets even weirder with copyright, being part of a torrent swarm as uploading part has regularly been ruled as "commercial distribution".

These are specific examples, and as mentioned there are an infinity of cases.

I am not sure they are grey areas. For example, in general anything you do as part of your job at a commercial enterprise has a commercial purpose.

Well, see, I'm reasonably comfortable with using NC so long as I'm not selling or being directly paid for something. Otherwise, pretty much everything I have in public is associated with my job at a commercial enterprise or other business in some manner and I effectively can't use NC for anything non-trivial. So, without surveying the rest of HN, we already disagree on a wide swath of use and probably wouldn't change each other's minds.