Hi,
I'm just starting out with my own Mark IV, so I'll share what I've learned so far.
As Aikidokajeff said, first remove the line:
172.16.42.1 *
Then you can create entries like this:
172.16.42.1 *.facebook.com
172.16.42.1 *.twitter.com
All traffic to other domains will go through unintercepted. You can verify it's working as intended by looking at /www/pineapple/logs/dnsspoof.log.
Hope this helps!
-c0