Maybe it's a bugbear of mine but we seem to have had a lot of spamming recently; from tiny one-man operations in the far east to employees of large vendors peddling their hardware. It's easy to delete their posts and even suspend them but to be fair to them our policy in this area isn't clear in the FAQ - should and could it be clarified?
Since when spam needs to be explicitly forbidden?
It goes without saying, in my opinion. This is a Q&A site, there are advertising possibilities on it, it's pretty clear that questions and answers are not the places for people to advertise their products.
It would be also useless to make such a line in the FAQ. It won't prevent any spammer from posting their stuff. I don't think there is a need to be "fair to them".
Maybe your situation differs from Super User in that you get more "corporate" advertisement, but the effect remains the same. There is link for advertisers at the bottom. If they just want to spam their product links, it shows that they don't care and just want some free exposure.
About spam in general, I have found mostly two kinds :
the robots: the ones who have a site/product to promote, often of bad quality, and will simply answer to all related questions, even the ones which were answered and sleeping for 6 months, with their link and a basic description. No discussion to have with these ones, from what I experimented. You can try to leave a comment to see if they react, they never will. On SU, we used to simply destroy them on sight. Now we do something more valuable and aesthetical: we fuse them into one inert monster/piece of art.
the traveling salesmen: they actually work(ed) on the product they are advertising, and are acting like a regular commercial. Answers will be more adapted to the questions, and they will sometimes post actually useful answers using their product. This kind is more likely to actually answer to comment. It's ok to give your own product as an answer once in a while, as long as your contribute in other ways. For the ones who are actually only writing about their product, they should be reminded of the "advertising info" link at the bottom, and warned that they are on the thin line to the "robot" behavior, and face the same fate.
All FAQs now contain an explicit message about advertising (thanks Jeff):
May I promote products I am affiliated with here?
The community generally frowns on overt self-promotion and tends to vote it down and flag it as spam, so be careful. Post good, relevant answers, and if they happen to be about your product, so be it. However, you must disclose your affiliation with the product in your answers. Also, if a huge percentage of your posts include a mention of your product, you're clearly here for the wrong reasons. Our advertising rates are quite reasonable; contact our ad sales team for details. We also offer free vote-based advertising for open source projects.
Not that it's particularly easy to find - but in the footer is a legal link.
A Note from the Team
... Spam, personal attacks, and abusive language do not have a place on the Stack Exchange Network. If you ever stumble across anything on the Stack Exchange Network that looks like it violates our policies, please be sure to let us know.