I'm unsure if this anecdote will be helpful to you, but it's the best I
can offer. During Christmastime, my large, extended family has a big get
together with a fun gift game. All the presents get piled in the center
of the room. Some of the presents are silly joke gifts, but others are
quite nice. Everybody gets a number. When you get your turn, you can
either pick a wrapped present from the pile, or steal a present from
someone who's already opened one. Each present can only trade hands
three times. All sorts of deals and conspiracies follow, but it's a lot
of fun.<p>This year, one of the kids, a boy about 13, got a pair of battery cases
for two different iPhone models. Though he had an iPhone, he <i>REALLY</i>
wanted to get rid of the battery case so he could pick another gift. I
played the part of the "too kind grown up" and "stole" the gift he was
vehemently flogging. I don't own an iPhone but I figured I might be able
to use them for parts for some electronics project (you can never have
enough spare batteries and widgets ;). The battery cases were actually
good, band name (Duracell I think) accessories, but absolutely nobody
wanted them.<p>As much as people complain about phone battery life, if you can't get
anyone in a group of adults and especially kids to want a free battery
case, there may be some issue with the product.<p>Though battery cases make sense to you, and me, I've never been a heavy
mobile user, so I've never had the need for one.