There are pickpocketing in HK as in any major city but it is not a serious issue. Be careful at crowded areas such as crowded trains and platforms.
Statistically, HK police reported a total of 940 pickpocketing cases in 2008 and 1,198 cases in 2007.
(Source:
http://www.police.gov.hk/hkp-home/en.../compare08.htm)
Pickpocketing is a more serious issue in Shenzhen than in HK.