I still not made any transaction here since I have just started to earn few hundreds buck here.
I did donate to BMF because the owner asked for the members to help to pay for the fee of removal an advertisement banner, if not mistaken. I donated 1,000 points or USD1.
I haven't donated my points to charity, but I did donate my points to someone on another site that I knew would use them since I was leaving the site and I didn't have enough for a cash out anyway. I figured the other person could use them more than me. Now that I think of it I have done that on a couple of sites.