I have a client who has a competitor that has consistently copied my client's articles (even officially copyrighted) and press releases, etc and falsified the names and urls in those articles for over 2 years now. The competitor had also set up several freebie websites that copied my client's website which we easily had removed. However, we wasted a lot of time getting those sites taken down and proving ownership of articles and press releases posted elsewhere or having them taken down.
My client recently sent in a DMCA to Google including correspondence with this crook and proof of years of dealing with this crook (about 100 pages full of proof). The competitors articles and press releases are now disappearing off the net and even the competitor's main website (which the compeitor had carefully not copied any data onto) has dropped in PR and now has only 2 pages in Google's index.
So DMCA works, if enough proof is included.