I guess the 'good' spam doesn't look like spam. I'm constantly perplexed at how counter-productive most spam, in whatever context, is. It just screams - I'm tacky and unreliable and I want to steal your money!' If you've got a good sales message and you deliver it professionally, I suspect most people wouldn't immediately think of it as spam, even if they hadn't actually asked for it.
wholesale forum spamming no, but highly targetted forum spamming - well, yes in some instances. Lets just say that you have just invented err,,,, the greatest mop of all time. You would want everyone at cleaning forums to know about it so that they bought one. Would registering at each forum for cleaners and doing a 1 post that informed them of this new product spam? Well probably, but it is reasonable spam IMO. If your just registering at random forums to submit links, then this is NOT acceptable. Back to thread topic, if your email spamming you will probably be highly unpopular - its a crime in the US and its a shame it isnt in the rest of the world.