So, it appears that I’m not the only one grappling with how to cope with duplicate content issues and content replicated in different places.
The session on this issue at SES attracted a sizeable crowd and a whole clutch of questions at the end.
Mark Jackson (of Vizion Interactive) gave a lively presentation with useful tips. If you are worried about duplicate content, check how many pages you have listed in Google and compare this with Yahoo. Normally there will be some discrepancy, but if the variance is large, you may well have a problem. Copyscape offers a great service to try on a page-by-page basis.
For your own site, you should where possible use unique titles and meta-descriptions. Google Webmaster Tools can help you see where you have the same meta-descriptions.
If you do notice a problem, the best course of action is to approach the site owner directly. If you have no joy here, you can file a DMCA with the host of the offending site, or with the search engines directly.
Benu Aggarwal (Milestone Internet Marketing) made the point that these days you can’t necessarily trust copywriters to write unique copy. She points to the iThenticate service as a good way to establish the similarity between your copy and what has been indexed.