One of the problems with shared webhosting is that modern script languages as PHP, Python or Perl are to powerfulpowerfull. They can read almost every file on the system. There are some tricks to prevent some of this, but it is not an easy task. All to often a knowledgeable person can find backdoors because of the vast amount of possibilities these scripting languages offer. The ultimate solution is to lock all the webhosting accounts in there own environment. OpenVZ is ideal for this.