[Sip] Notifier Privacy Mechanism puzzle

[Y01317@njupt.edu.cn]

Hi all, 
  I have a question about section 5.2 Notifier Privacy Mechanism in RFC3265 
  <quote> 
 The mere act of returning a 200 or certain 4xx and 6xx responses to
 SUBSCRIBE requests may, under certain circumstances, create privacy
 concerns by revealing sensitive policy information. 
  </quote> 
  I do not unstand why it says a 4xx or 6xx response can reveal sensitive 
policy information, for example, the notifier send a 403 Forbidden or 401 
Unauthorization , can this cause policy problem? I think no. If it can , 
anybody give me some explanations? 
 Thanks. 
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