I believe you still can use StreetPass with it. SpotPass though is disabled for it, so you can't use it to send out mail to friends that aren't near you.
It's most likely a desperate short term solution to prevent parental outcry. Though, it doesn't really solve any long term issues. Any online experience will have any child succumbed to potential inappropriate material. There is really nothing Nintendo can do to protect minors from everything, but only make it inconvenient for anyone to have any social interaction.
Such as, what prevents a person in making a ACNL patterns that depicts inappropriate images? Nothing.
What prevents a person from sending inappropriate ACNL messages or town board messages? Nothing.
Simply put, you can only control so much...
You can only protect a child's innocence for so long.
http://penny-arcade.com/comic/2012/11/30