At WDW the DAS is generally issued for the number of people in your party -- up to 5 plus the DAS holder. It is possible to get one issued for up to 10 guests (9 plus the DAS holder), but this requires supervisory-level approval and everyone in the party must be present at Guest Relations when requested.
At DL/DCA, my understanding is the standard DAS is for a total of up to 4 guests. As at WDW, it can be issued for a larger party with approval and all guests present.
For the OP, if you haven't checked it out, there are 2 DAS information threads stuck near the top of this board. One is about DAS at WDW and the other about DAS at Disneyland.
The first post in each thread is a DAS FAQs.