I've usually been thanked in some way (for what little I can spare), unless it's anonymous such as stuffing a little sumpin' in the donations box for RGS 20. The Friends of the C&TS have always put a friendly (it's in their name!) little note on a receipt for the hat proceeds donations or Dorman purchases.
On the other hand, I ask for a lot, from individuals and institutions - photos, drawings and such, always clearly stating I'll pay for the trouble if it's not easily purchased or available. I never presume to get something for nothing, and costs are usually reasonable (that is, worth it to me) and I'm willing to wait. I've joined organizations or donated to such if it helps, doesn't always but sometimes... and why not be a nice guy anyway... But I can't join or donate to everything I'd like.
Mike