For me, a forum post is spammy if the person keeps dropping their link as the only possible solution for whatever is being talked about. Usually, the same member drops links all over a forum or blog and recommends no other products. That comes across as spammy marketing and makes me think of the person as being disreputable. Another way of being spammy is by contributing the least necessary in a forum post or on a blog comment and still leaving a backlink. If you're on a site, at least give quality content so you are helping others out. What's your idea of spammy marketing? And, how does it make you feel when you see someone being spammy on a forum or blog?