Honestly, I think the best solution to letting friends try out ecigs is by buying a bunch of cheap pass
throughs. Why worry about friends draining or mess around with rechargable
batteries. It's cheaper than buying spare PV kits anyway and all you need to worry about are atomizers. This way, if they really want to have their own battery PV they can
buy it themselves and spend the money on it.
As for strangers, I don't really let them use it mainly because I'm impatient and hate being stopped in the middle of what I'm doing to sit there and give lectures on it. I'll pass cards out though. I always carry several blank carts on me so if I'm really nice to let someone try it out it's not a big deal to waste a cart on them at least.