The Russian government urgently needs to obtain full membership of the World Trade Organisation in order for their country to meet its full economic potential.
It can't get that membership without the support of the USA. In order to get that support, Russia has entered into a bilateral agreement with the USA which means that it's committed to closing down internet sites which breach intellectual property rights.
http://www.ustr.gov/assets/Document_Library/Fa ct_Sheets/2006/asset_upload_file151_9980.pdf
So it's extremely likely that the Russian government has 'pulled the plug' on Mp3Sugar.
Chris