Can you make Search Engines ignore a custom Region?

I understand how to add a custom region to a theme. My question is what can I do to make the Search Engine robots ignore that region? For example, when adding a promotional block to MyPromo region, such as for Amazon or GoodSearch, I do not want the Search Engines to view it as content.

I had this happen in one of the contributed themes. I had added a promo block in the Sidebar region and when you Googled our organization, the text from that promo was what displayed as our description.