As to the questions regarding sex offenders on social networking sites:
There are only three states that create felony-level statutes for "sex offender presence on a social networking site: Illinois, New York, and North Carolina. Louisiana is one other state that had a law, but that law had been struck down by a federal court (Clinton-appointed judge) because it was deemed to broad. As written, basically ANY site that required a profile, even tangentially, would have been outlawed. This would include email accounts associated with companies that also have social networking sites, such as gmail, yahoo mail, and aol mail. They are in the process of rewriting the law to specify social networking sites; however, the ACLU is planning on filing AGAIN based upon the senate-passed text of the new law.
I believe that this law should be federalized into SORNA, and furthermore, that there be a federal statute that designates ALL such usage. The reason that it must be at the federal level, and not the state level, is that the Internet is typically interstate/international in nature, and local laws cannot possibly keep up with the myriad of circumstances that come with incidental use of the Internet by RSO's. There are too many ways the ACLU can fight these laws the way the statutes are written. But if the laws are written into SORNA, that would take the regional federal courts out of play and force significant changes into standardizing the elimination of RSO's from the Internet.
However, that's neither here nor there. The second major issue is that Facebook and other sites have methods in which they can delete accounts of sex offenders. However, I BELIEVE THAT IS NOT ENOUGH. I believe that if there is confirmation that a sex offender has been found on a site, they should be able to immediately send such information to the AG office of all states the offender is registered in, as well as the states of any minors that are "friended" on the list for investigation. Furthermore, they should make it a CRIME for Facebook to delete the information without confirmation from the AG's of the states. (Yes, they can certainly restrict access, but they cannot delete the information.)
By the way, I am of the opinion that every sex offense involving children should be treated as a FEDERAL crime, even for local cases, for the very purpose of standardizing punishment and registration. When the myriad of state laws muddy the mix, we have the problems in which you see now, with jurisdictions not prosecuting obvious slam-dunk convictions of RSO's on Facebook in states that specify felonies for those offenses.