This is a very interesting video from Matt Cutts about who gets credit for content when someone steals your content.
If you wrote content, someone steals and changes a date stamp to appear that they were the originator of the content what can you do. Matt addresses several scenarios in this excellent video.
First, Google will try to see who is the content owner by not only the actual content, but by co-citation on the web. I personally feel this is also why posting your blog out on Twitter and Facebook is important to link your content to your own web properties.
Second, taking time to let other sites know via a DCMA notice that they need to remove your copyrighted content although time consuming can be well worth the time. I have actually had web hosts take down full websites until the owner removed the infringing content. That is sure to get a thief’s notice when they will not respond to your take down notice!
If you can’t see the YouTube embedded video from Matt Cutts watch it online at YouTube.
Third, consider using PubSubHubBub protocols to push your content from your blog out to interested parties tagging your content early on the Web before scrapers can get it.