Well about Google's interface of newsgroups, I can say it has saved my life, since my ISP's news server (which, ironically, they dont know they have!!!... yeah, its a long story, I'll explain in another post) has crashed, or something, the point is that when I open the news with my email client (well I am not spamming when I say... Mozilla Thunderbird! :) it is just blank, well anyway...
I want to say that I agree with my pseudo-anonymous friend (well I just know you're "ekstesi@g..." :) and I want to add something interesting that I just thought while I was typing this post... if you do any kind of advertising with OSS, for example, a typical line in your signature, under your name, like "Linuz Rulex" or "Firrrrefox!!!", or a post talking about an OSS project, well far from being annoying, people will think you're cool, some Guru of OSS (and maybe you have nothing to do with any OSS project), meanwhile, if in your signature you got something like "God Save MicroZoft" (and hey!, this is just an example, I dont intend to offend anyone : ) some people will consider it some kind of spam, even if you dont work with this company and you're just a fan (drunk, ehem :).
Funny indeed it is... you can go to any group and post something about OSS, talking about a project you're working on, asking people to try it, etc, you have few/null chances of being flamed or called spammer.
So we can say, only if your ad is of non-commercial nature you'll not be flamed? Well this is not completely true, its not only if it is related or not to the group you're posting, but also about WHAT you're advertising. For example, go to misc.health.alternative and post one of those emails we receive every day about those "cool pills" for losing weight, or for "helping" guys :)... and even though its perfectly related, well they will probably ban you...
By the other side, it is possible to advertise something in all groups and not be considered spam, as long as what you're advertising doesnt offend anyone and you are not repeating it annoyingly...
So the definition of spam becomes kind of complicated... I would extend your definition to "repetitive non-relevant or offensive information".
And finally, yeah I guess this is a crazy topic to talk about in a VoIP group, I know, I started it, but it just became interesting and fun (at least I had fun).
Now I feel my question has been answered so thanks!