The Hong Kong Government has amended the Personal Data (Privacy) Ordinance which will be effective from 1st April 2013.
Marketing SMS communications may only be sent to consumers who have explicitly consented (opted-in) to receive this form of SMS communication. Failure to comply with this requirement may lead to the imposition of significant financial penalties and imprisonment.
More details can be found in the following newsletter issued by Office of the Privacy Commissioner for Personal Data (PCPD), Hong Kong. http://www.pcpd.org.hk/english/publications/files/newsletter_27.pdf.