In reference to this other meta question:
I would encourage people to avoid using spam flags for posts that have zero constructive comments, zero down votes and are not actually commercial promotions or offensive speech. [emphasis mine]
I expect those of us who use the flagging system work from a standpoint of "I'll know it when I see it" — but we don't all see things the same way in the face of ambiguity.
As a moderator elsewhere in the SE network, I've developed a somewhat low threshold for considering a post spam, and since I hang out here too I consider it my civic responsibility to put my nose to good use. (Actually, I really just want a shiny Marshal badge. :)
So, under my thinking: If a new, mostly unidentified, unregistered, 1-rep user posts an answer to an old question, and the answer mentions/links to a commercial product or service, or a sketchy blog/article linking to such, my shit-detector goes off.
I ask myself: Why, out of the blue, did a completely new user come to the site and post a commercial link-containing answer to an old, already-answered question (i.e. quite often not a question on the home page) for a problem they aren't having?
The simple explanation is it's a spammer using a targeted search for places to astroturf. Since most spam are one-offs, I often don't wait for a pattern to emerge. This isn't a criminal court, and presumption of innocence isn't necessary. I work on the balance of the probabilities. Deleting a seemingly spammy post isn't the death sentence.
But that's me. I've had some flags rejected. Maybe I'm too quick to judge?
So: What is (or should be) the objective criteria or definition here at Ask Different for considering something spam or commercial promotion?
If the current standard is tacit, can we work to write it down? If there isn't such a standard, can we work to establish one? What do you think of the criteria I mentioned above? It's easy to recognize obvious spam ("Buy now! Operators are standing by!") and also spam where there's a clear pattern, but what about quick & subtle one-offs?