I just assume people PIF if possible and we rarely know. I believe we should give with a happy heart and it sounds like that is what you intended. Imagine researching to find a family member - how awesome are you. That was such a neat idea.
I will say I have only been on the board here a few months and have sent fabric, patterns, scraps, etc. to probably 10 people now. Only 1 has offered to pay the postage. I was not offended as no where in the request did they mention they would pay postage they just asked if anyone had any to spare. I hope I've never accidently offended anyone because honestly if someone I did not know contacted me and offered to send me something it would never occur to me to offer her the postage back. I'll remember that for the future though.