There seem to be two approaches to doing trials. The traditional one is having users enter their credit card, giving them 14-30 days of free trial, and charging them after the trial ends.
The other approach is to use credit cards just for signing up (to avoid bots and stuff) and don't charge after the trial ends.
The other approach seems better to me, because I think that it will make users feel like they're not being forced into anything. But at the same time, I think that the first solution makes users not forget about you. If they sign up for a trial and know that they will be charged after 30 days, they'll make use of the trial to decide if they should cancel their subscription or not. If no thing's forcing them to do this, they can just sign up, click around a few times and then never use your app again.
So the cancel-subscription approach is more "morally" appealing to me, but the charge-after-trial might be more practical.
Although I can imagine that users churning after using the app for a few minutes and not going back unless forced to by an upcoming payment is a sign that your app is not engaging enough. So the charging approach can often be a compensation for bad app experience.
What are your thoughts?