...found this oldie but goodie and thought I would share; after spending a lot of time trying to remove duplicate content/titles/etc (e.g., ?start=10, ?start=20, ?state=50 table filters all sharing the same title, for example), I think it was all for naught:
Duplicate content. There's just something about it. We keep writing about it, and people keep asking about it. In particular, I still hear a lot of webmasters worrying about whether they may have a "duplicate content penalty."
Let's put this to bed once and for all, folks: There's no such thing as a "duplicate content penalty." At least, not in the way most people mean when they say that.
... •If you're a webmaster of beginner-to-intermediate savviness, you probably don't need to put too much energy into worrying about duplicate content, since most search engines have ways of handling it.