Ant writes in to mention the World Privacy Forum's top ten information collector/user list, which shows opt-out instructions (or at least a starting point): "As privacy experts, we are frequently asked about 'opting out,' and which opt outs we think are the most important. This list is a distillation of ideas for opting out that the World Privacy Forum has developed over the years from responding to those questions. ... Many people have told us that they think opting out is confusing. We agree. Opting out can range from the not-too-difficult (the FTC's Do Not Call list is a fairly simple opt out) to the challenging (the National Advertising Initiative (NAI) opt out can be tricky). Our hope is that this list will clarify which opt out does what, and how to go about opting out. In this list, some opt outs can be done by phone, some have to be sent in a letter via postal mail, and some can be accomplished online. Some opt outs last forever, some have time limits, and others can be changed at will. If an opt out is on this list, it is because we thought it might be important enough to be worth whatever annoyance it may pose. "