Militants are being encouraged to use the online site through postings on other Islamic forums on the Internet. Wednesday, December 3, 2008 WASHINGTON (Reuters) - Islamic extremists are being instructed on how to use the popular video-sharing site YouTube as a way to disseminate propaganda videos, a U.S.-based terrorism monitor said on Tuesday. Militants are being encouraged to use the online site through postings on other Islamic forums on the Internet, according to the SITE Intelligence Group. Last week, an extremist authored step-by-step instructions on posting video to YouTube, which he described as "one of the most famous and biggest...