Source:
Computerworld... Another kind of "spam" occurs in open message boards, or in user-ranked content services like Digg. Some companies or organizations that want to "astro-turf" an opinion or idea may send legions of fans, employees or paid posters to overwhelm a topic with that point of view. One of the best known is the Chinese government's so-called 50 Cent Army, which involves thousands of people paid to post pro-Chinese Communist Party opinions on message boards and social media sites inside China and around the world.
The Chinese government's well-organized effort overshadows the more informal actions of many organizations that do something similar. Many large multinational corporations encourage employees to go out on the social networks and message boards and say nice things about the company's latest initiative. Some smaller companies use this technique as their main source of marketing.
... The major social networks and search engines are fueling the trend. Google and Bing offer limited results on some searches based on what your Twitter, Facebook or Buzz followers have posted. The idea is that if you're looking to buy something, your peer group or loved ones are both more relevant and more trusted.
And that's why your social graph is the next ripe target for shady marketers. As services increasingly enable you to search for things influenced by your social graph, spammer types will try to infiltrate your social group and sway the results.
Read more:
http://www.computerworld.com/s/article/9200820/Elgan_How_spammers_will_poison_your_social_graph