>Anyone else familiar with the derogatory usage? Is this an area where perhaps British and US usages differ?

I'm guessing that the derogatory usage started in the U.S. and predated the Brownies co-option of the term.

p.s. - I've just discussed this with an ex-(US)-Brownie, and she claims they never earned Brownie points, but rather awards -- maybe it's the Brownie Points that are a UK usage.

she also tells me that Girl Scouts is US and Girl Guides UK, but Brownies are junior divisions of both.