This is probably the biggest nightmare of any web publisher – a scraper site outranks you (the original content owner) in Google by using your own titles and excerpts. Mahalo, Clipmarks, etc. are some examples:
What Mahalo does is take snippets, and publish them as content on their site. So they use your page titles and your content snippet to rank their site using your content, without your permission.
If you optimize your page titles on a new blog post you are helping to feed relevant optimized content into the Mahalo machine. They will scrape it, and if you are less authoritative than they are, they will likely outrank you!
To add further insult to injury, they put nofollow on links back to the content source which they are scraping content from, so while they are “borrowing” your content you are not getting any link credit for it. link.