It's not really an issue unless they outrank you or rank near you.
In my experience, Google's dupe content detection is pretty good and their penalty is harsh. I once ran a website that tried to curate and touch up old usenet material that never could rank all that well because of dupe content (another website had monospaced dumps of the usenet content).
In my experience, Google's dupe content detection is pretty good and their penalty is harsh. I once ran a website that tried to curate and touch up old usenet material that never could rank all that well because of dupe content (another website had monospaced dumps of the usenet content).