"... There will be a Web equivalent of 'No shoes, No shirt, No service'," says author and tech futurist Paul Saffo. In other words, if you want to join the club, show your card.

Second Life is tapping technology called Integrity, from Washington D.C.-based Aristotle International. Soon only those Second Lifers willing to divulge their social security numbers (or passport data) will get access to content that other members have flagged as "adult."