First of all, a little bit of history. Since the mid 1980's I've been very active on newsgroups and forums run by CompuServe and Microsoft. In fact, since I became a self employed consultant. I give out a lot of information freely and I've always made an effort to explain the principles behind my answers rather than just paste a link to somebody else's answer or tell somebody where to look in the help file. Furthermore, I maintain a web site with comprehensive articles, extensive code in both C# and visual basic which is used as a resource by literally thousands of engineers all over the world.
I discovered many years ago that helping people out for free can be advantageous because people often contact me afterwards and offer me contracts, both short and long term, and even fulltime employment in their companies. As a consequence, I am able to make a living through the Internet and those forums and newsgroups which I frequent are often the primary point of contact between me and my clients.
Whenever I post in a newsgroup my signature carries links to my website, articles and products. This has always been the case. Furthermore, I often post announcements to my products and services which are clearly marked as such and are easily filtered by those people who do not wish to see such announcements by the simple expedient of a filter that removes the subjects tagged with a ANN: prefix.
Recently, I was given the MVP award by Microsoft, largely for my work on the newsgroups but significantly, for the content of my website and my advocacy of Microsoft products. This is to say that my practices are certainly not incompatible with the Intent of the Microsoft public newsgroups. Indeed, I am somewhat surprised because having been recently singled out by members of a newsgroup because of "unacceptable practices" I looked back through the newsgroup archives to discover that there are numerous announcements for commercial products from other MVPs and companies which have drawn no comment whatsoever.
One thing I will not do is to be drawn into a public flame argument on a newsgroup. I have a comment section on this blog and anyone is free to put whatever they like on there.