Mail adresses used on this site, and only (exclusively) on this site (not only me, I know about two other cases), have started to recieve spam. What happened?

The spam (always the same), comes from "Walinda Textile lilewoo_md@yahoo.com.cn", and goes like this:
"Dear  Sir/Madam,
It is my pleasure to write you in respect of our Company Wujiang Wanlida Textile Co., Ltd.
Based No.6 The Third District Nanshan Road, Shengze, Wujiang City, Jiangsu Province. China. We are experts in the sale of Textile  materials; we export into the Canada/America and parts Europe. We are searching for representatives who can help us establish a medium of getting our funds from our costumers in these areas..."
and so on, a classic scam know as nigerian scam (we need someone to handle money for us, you'll get some, but you'll have to pay some unexpected expenses).
The question is, how have those scammers got hold of addresses only Renderosity is supposed to know?