That's what Jeff Perron argues. Homeless teens have no fixed address (obviously) and no way to be contacted, which makes finding a job very difficult; mobile phones allow employers to contact them. Perron argues that mobile phones also allow agencies to mass-text health information and services information.
Perron makes a pretty good argument, one that will sound better as mobile service costs drop (assuming they actually do) and especially if SMS costs drop. I'm interested in how this argument seems to be a continuation of universal service (in its second aspect, that of providing inexpensive access to all interested households).