Let the hive mind of Engadget get that for you.
"I just switched to Sprint from Verizon about three months ago for the Pre. Then I went for the Hero about a week ago. Now, I miss my hardware keyboard and am thinking about switching to the Moment. I am still able to switch back to Verizon if I want and get the Droid when it arrives. Should I just trade up to the Moment when it comes out, see if I like it, and if not switch to the Droid? Or something else entirely? Help!"
Working in the Civic Center of San Francisco and living in SF in general, I see a lot of homeless people on a daily basis. Yes, I've seen cell phones and even ATM usage but unfortunately not as much as I've seen needles and crack pipes.
As for how they keep them charged, when you sleep on the street and basically got nothing you tend to get pretty resourceful. Most people don’t know that if a bus shelter has lighting, it has a good chance of having an electrical socket somewhere out of sight. Or they could plug in at the library or on the occasion that they stay at a shelter. But if you were to walk around in any given city and really looked around, I bet you would find dozens of publicly accessible outlets.