According to Mashable, the YouTube-style service is called "Mehr," the persian word for "affection." YouTube has been censored in Iran since 2009, when it plays host to more than a few videos of brutality against voters. Signs of the new Iranian shadow-internet have been slowly appearing since October, with secondary IP addresses being assigned to a large number of Iranian computers.
Iran is second in internet censorship and oppression only to China, though North Korea is also entering the digital sphere with a local-only national intranet that allows for no outside access. Much of both Iranian and Chinese internet censorship come from an intense combination of legal measures, social pressures, and technological innovations to suppress and shape online expression.
Iranians have been cut off from the greater internet several times this year; it will be interesting to see how the Iranian government manages the peoples' transitions from a comparatively free internet to a deeply suppressed, national intranet.