Simsi - 11:02 am on Jun 7, 2013 (gmt 0)
Austtr: But if I actively encourage people to write articles to publish on my site because I want to supplement my content with additional material from subject experts, do my article pages become advertorials because I provide an acknowledgement and links back to the author?
In my opinion, *any* external link to your website that you can influence the placement of is effectively an advert for your site, regardless of the intention and especially if your site is commercial. If it is surrounded by text is irrelevant but if it is, and that link was placed by arrangement and again your site has a commercial angle, it is open to be labelled an advertorial.
The good thing is that Google's algorithms aren't good enough yet to detect them all so webmasters and SEO companies can continue to exploit this "loophole" in Google's intelligence if they wish to. Long term though, you have to assume that link will be discounted and that your ranking could accordingly be re-adjusted. If you or the person owning the site where that link is placed hasn't been very diligent and ends up getting flagged for this practice, it may even end up penalising you.
It's risky to a long-term strategy to go down this "supplemental content" route in my opinion.