Good, this is a great way of filtering out terrorists and extremists while letting ordinary people through.
Many extremists continue to promote violence over Twitter, the government should 100% be investigating these people's Social Media accounts.
The only nonsense here is that it's "Voluntary" and that they rely on them to provide it. Tapping their lines once they're in the country until they become a legal citizen is a better way of monitoring this and still protecting the rights of U.S. Citizens.
People like the New York Truck attacker used social media extensively to promote and plan their terrorist acts.
http://www.bbc.com/news/world-us-canada-41835266
"Our gaze naturally turns, then, to the source of his radicalization, to where he so easily found the ISIS material: Facebook, Twitter, Google and YouTube."
http://time.com/5008076/nyc-terror-attack-isis-facebook-russia/
People pushing such content shouldn't be allowed in the U.S., and if they are they should be rounded up and executed for planning to commit terrorism.
People from Terror ridden countries and countries without strong immigration policies shouldn't be "asked" to be provide such details - they should always without question be monitored.
The only flaw in this is the optional component.