There is no such thing as being too generous with weed (for me anyway)... I only smoke with my 2 closest friends, and it's ALWAYS my weed (hell, one of them knows she can call anytime, and I'll drop off a gram or 2 for free). Pot is one of the things I "bring to the table" in our friendship. They have other things they "bring to the table"... One fixes mine and my family's cars, and helps me do home repairs that are too big for me to tackle on my own (for free). The other is my lifeline. I can call her anytime I need to about anything. I can also eat or drink for free where ever shes working, she buys me little gifts whenever she can, and she always tells me how much she appreciates everything I do for her. I would take a bullet for either of them, as they would for me.
I don't share weed with people based on how much they can share back, I share with them to help enrich their lives, because they enrich mine.