In mid-2013, a problem occurred that slowly began unmasking the hidden registration information for owners’ domains that had opted into WHOIS privacy protection. These domains all appear to be registered via Google App , using eNom as a registrar. At the time of writing this blog, there are 305,925 domains registered via Google’s partnership with eNom. 282,867 domains, or roughly 94% appear have been affected . (Google reports that new domains which have not faced a renewal period are not affected and many businesses do not opt into their privacy service.) The information disclosed included full names, addresses, phone numbers, and email addresses for each domain. The information was leaked in the form of WHOIS records.
More Details : http://blogs.cisco.com/security/talos/whoisdisclosure