A favour is a personal request from a friend, I can't see this is an area that needs to be made more efficient...
Por Favor aims to fill the space where it's a small favour, like turning on the oven at a certain time or taking out the bins. Things that aren't too much of an inconvenience but are also easily forgotten.
You mention tracking favours, that's definitely not what it's about. It's about remembering to do things you said you would, not about keeping score.
This is the copy that's making people think along those lines. If it's sending the wrong message then this is the bit I'd change.
@ollysb, @nodata: Sorry about that. I was honestly confused why people thought it was about keeping track and kept bringing it up when I'd said it wasn't. Now it all makes much more sense