The drawback is that they're also likely to turn themselves into a legal organization as this "advantage" gets exploited to its limits. It will also draw them into a tight relationship with the U.S. Government, the same one that they're now proud to have defeated. This is because only those with enough resources to repeatedly subpoena information from the registrants. In other words, Microsoft and the USG. The rest of us security types are left out in the cold.
Unless ICANN starts policing the environment they control, allowing people to hide behind false or hidden identities, I wouldn't be surprised at the type of law suits they'll face in the coming years, especially if the situation gets so bad that government feels the need to step in. This will get quite interesting in the next few years.