Primarily social networks are made by people for the people. They're a place where members can make new connections and interact with each other about common interests. From my experience they are generally really friendly and welcoming environments presumably as everyone has the same motive. To exchange ideas, share knowledge and advice and also get a sense of belonging in a close community. This obviously becomes harder as network sites grow in members though threads are a good way to keep the feeling of a small community.
Brands need to take into account this type of environment when they look to get in line with the social network trend. Any attempts to use them as just another advertising space to sell their services direct to people will almost certainly be met with a hostile response as they are not respecting the site or the members who use it.
Instead of being a corporate mouthpiece for the brand, marketers need to think about using more personal tactics. They are more likely to be accepted if they come as individuals with their own contributions to the discussions.
Most networks like new members to introduce themselves to the group and reveal a bit about themselves. This is because users value transparency and are looking to build valuable long term relationships rather than be hit by various impersonal sales pitches.
Spam as its referred to, is negatively received by the majority if users yet brands still insist on posting them. Surely this is bound to have a negative effect on their image. Though as long as people are still curious enough to click on the links, they are still likely to exist but I think e-marketing should hope to take the long term view more seriously using the principles of relationship marketing, building a reputation of original thinking and expertise in problem solving through as they partake in these forums.
Social networks, contrary to popular belief, are here to stay. User generated content has taken off and shows no sign of slowing down. Consumers are liberated and are not likely to hand back control to brands easily any time soon so it is time for brands to wise up and play by consumers' rules and become TRULY consumer orientated.