Islam mandates death for non-Muslim subjects of the Islamic state who mention "something impermissible about Allah, the Prophet (Allah bless him and give him peace), or Islam" ('Umdat al-Salik, o11.10), and such laws go back to passages in the Hadith and Sira in which Muhammad orders the murders of people who have insulted him, including Abu ‘Afak, who was over one hundred years old, and the poetess ‘Asma bint Marwan. Abu ‘Afak was killed in his sleep, in response to Muhammad's question, “Who will avenge me on this scoundrel?” Similarly, Muhammad on another occasion cried out, “Will no one rid me of this daughter of Marwan?” One of his followers, ‘Umayr ibn ‘Adi, went to her house that night, where he found her sleeping next to her children. The youngest, a nursing babe, was in her arms. But that didn’t stop ‘Umayr from murdering her and the baby as well. Muhammad commended him: “You have done a great service to Allah and His Messenger, ‘Umayr!” (Ibn Ishaq, 674-676)

Then there was Ka'b bin Al-Ashraf. Muhammad asked: "Who is willing to kill Ka'b bin Al-Ashraf who has hurt Allah and His Apostle?" One of the Muslims, Muhammad bin Maslama answered, "O Allah's Apostle! Would you like that I kill him?" When Muhammad said that he would, Muhammad bin Maslama said, "Then allow me to say a (false) thing (i.e. to deceive Kab)." Muhammad responded: "You may say it." Muhammad bin Maslama duly lied to Ka'b, luring him into his trap, and murdered him. (Bukhari 5.59.369)

"Man allegedly stabbed over prophet insult," by Lauren Turner for AAP, December 3 (thanks to Lachlan):

A YOUNG man tried to stab his brother to death for insulting a Muslim prophet, a court has heard.
Safaa Allami, 22, is accused of attempting to murder his older brother Ali Allami during a row at their Cloverdale home in Perth's eastern suburbs.

Ali Allami was rushed to hospital with life-threatening injuries, prosecutor Nicholas Cogin said.

It is claimed... http://www.jihadwatch.org/2012/12/australia-very-religious-muslim-stabs-...