Legal and social consequences

Blogging can result in a range of legal liabilities and other unforeseen consequences.
Defamation or liability
Several cases have been brought before the national courts against bloggers concerning issues of defamation or liability. U.S. payouts related to blogging totaled $17.4 million by 2009; in some cases these have been covered by umbrella insurance. The courts have returned with mixed verdicts. Internet Service Providers (ISPs), in general, are immune from liability for information that originates with third parties (U.S. Communications Decency Act and the EU Directive 2000/31/EC).
In Doe v. Cahill, the Delaware Supreme Court held that stringent standards had to be met to unmask the anonymous posts of bloggers and also took the unusual step of dismissing the libel case itself (as unfounded under American libel law) rather than referring it back to the trial court for reconsideration. In a bizarre twist, the Cahills were able to obtain the identity of John Doe, who turned out to be the person they suspected: the town's mayor, Councilman Cahill's political rival. The Cahills amended their original complaint, and the mayor settled the case rather than going to trial.
In January 2007, two prominent Malaysian political bloggers, Jeff Ooi and Ahiruddin Attan, were sued by pro-government newspaper, The New Straits Times Press (Malaysia) Berhad, Kalimullah bin Masheerul Hassan, Hishamuddin bin Aun and Brenden John a/l John Pereira over an alleged defamation. The plaintiff was supported by the Malaysian government. Following the suit, the Malaysian government proposed to "register" all bloggers in Malaysia in order to better control parties against their interest. This is the first such legal case against bloggers in the country.
In the United States, blogger Aaron Wall was sued by Traffic Power for defamation and publication of trade secrets in 2005. According to Wired Magazine, Traffic Power had been "banned from Google for allegedly rigging search engine results." Wall and other "white hat" search engine optimization consultants had exposed Traffic Power in what they claim was an effort to protect the public. The case was watched by many bloggers because it addressed the murky legal question of who is liable for comments posted on blogs. The case was dismissed for lack of personal jurisdiction, and Traffic Power failed to appeal within the allowed time.
In 2009, a controversial and landmark decision by The Hon. Mr Justice Eady refused to grant an order to protect the anonymity of Richard Horton.
In 2009, NDTV issued a legal notice to Indian blogger Chetan Kunte for "abusive free speech" regarding a blog post criticizing their coverage of the Mumbai attacks. The blogger unconditionally withdrew his post, replacing it with legal undertaking and an admission that his post had been "defamatory and untrue" which resulted in several Indian bloggers criticizing NDTV for trying to silence critics.

source:Wikepedia