In the US, anyone can post/write/blog/etc. information about anything 'medical' they want, as long as they don't claim they are a doctor or try to see patients like a doctor generally speaking. That said, licensing in this country is on a state-by-state basis, as are most libel laws, etc. etc. So it can vary from state to state. The vitamin and supplement industries are also highly unregulated in this country with not approvals formally by the FDA, NIH, etc. All the best ones submit to outside auditing for the process, efficacy, etc., but it's not mandatory. And not all rating agencies are the same either.
But in general, you can write, blog, publish, etc. anything you want. There are tons of books written about all kinds of dietary and medical things by laypersons. At least for the Vit D research Steve has posted, it appears to be well researched, well documented, and backed up with links to multiple studies, etc. I've taken 5000IU a day for the last year and a recent routine physical with a blood test also checked for Vit D and B12 levels, and my Vit D level was right down the middle. Maybe it's not taken the supplement to do that, but I'd have to stop and then go back for another test, etc. For the pennies a day, seems no harm and anything I can do to stave off illnesses, etc. is welcome.
I know several medical professionals who are very competent IT people (and a few engineers in that to boot) so thank god for multi-disciplinary studies. Or we wouldn't have many of the life-saving technologies we have now that are highly technical feats of science, engineering, and IT skills.
If you don't want to take his advice, that's totally up to you. I for one, appreciate it and then I can do my own research and come to my own conclusions.
That said, this topic has now strayed a long way from just asking about Steve's Vit C findings....