For decades now, Word-of-Mouth has been identified as one of the strongest means of communication in marketing community. It started in 1970's when George Silverman - a graduate from Harvard University discovered it, while conducting a focus group discussion with few physicians and he noticed that one physician who was having good experience with drugs was able to sway the entire group of skeptics. From Harvard it reached Hollywood (where promoters and distributers started creating a hype of their up-coming movies in advance through Word-of-Mouth) and finally it landed into the world of retailing. They started using Word-of-Mouth to create a marketing buzz to amplify the original message of their marketing campaigns.
But there is another school of thought, where I come from. The matter of fact is that a simple tweet or a status update at Facebook is not at all 'direct'. It is more like professional bloggers from different companies, sending mails to - NOBODY. Well I (and probably many consumers like me) would not really like to be influenced by a 'mail to nobody' while making my buying decisions. The basics of the Word-of-Mouth influence is that you know the 'influencer', you have faith on him and you know that his/her recommendations are tried and tested in past. That is how it works, at least for me. The tweets, the Facebook updates etc. can create a cult to start with those early adopters but that cult can never be a long lasting one, unless there is faith involved in it (which is very less likely with a 'mail to nobody'). Also it might work with some products related to teens, who are kind-off care free and ready to try out new and different things. But in general, the effect of blogging is not even comparable to the effect of face to face Word-of-Mouth. Yes, people do want to see some feedbacks, reviews etc. from trusted people/websites as and when they are confused while buying a car for example. But they buy a new car just because someone at Facebook says that it is "cool" - that's highly impossible.
Well I am not the only one, skeptical about the power of blogs. Some time back Target also showed similar intent deciding not to recognize the blogs when a blogger emailed them criticizing a billboard. During the controversy Target emphasized that their marketing policy is to focus limited resources on the big media outlets, like television stations and newspapers (and not really the blogs), which reach large numbers of shoppers.
All said and done, e-marketer's study still shows that marketers are spending a-lot on the blogosphere but it would be interesting to see how much is coming back!!!