It generates an increased number of messages that people have to sift through. You can also get confused real quickly if two different people start giving you advice from two different directions, one in each thread.
I found the answer. Make sure your php is to asterisk:asterisk and to apache too. I found this very useful http://colt45.chemlab.org/?p=55 for a ubuntu 8.04 server. I am using freepbx 2.5.1 and asterisk 220.127.116.11