To be completly honest, iv'e never understood what this expression means, but even without understanding it's precise meaning, if there is one, something tells me i don't like it.

there is something arrogant in the notion that your mind is stronger than somebody else's without any visible avidence, and furthermore to use this advantage and get inside somebody else's mind, even if only for a brief moment, and make him think and say as you wish. But I have to admit that sometimes it's funny or necessary.

anyway, there are two things I wonder about:
1. how can you recognize a weak-minded?
It's obvious that you can't sense it, cause Qui-gon tried to use it on Watto a couple of times and gave it away after he sew it won't work. It seems that whenever a Jedi uses this trick there is this short moment of uncertainty (is it working? is it not?) untill the other person reacts. does that mean that you can't tell who is weak minded untill you tried to use the mind trick on him? if so, does that mean Anakin tried to use it on Padme and failed?

2. what does "weak-minded" means anyway?
Is it got to do with being force sensitive? but we know that Padme, Watto, Jabba and basiclly all the other main Characters are not weak minded, and they are not all Jedi.
Is it about intellect, wisdom? but even jedi and other people who suppose to be anything but weak-minded act stupidly sometimes or fall easy prey to lies when they're not using their common sense.

so, what is a "weak mind", and how can you tell when you see one?
I'd love to know!