Our former site was stolen (cut and pasted) at least a half dozen times, that I noticed. In all but one case, I emailed them politely about it - and they apologized and then fixed it. About half of them were in the USA, the others in Australia and Germany. Most of them took the whole thing, including links, text with our shop's name, and the pictures were still pointing to/hosted on our server

One guy even took our coupons!
We recently changed the site to something entirely different, because duplicate content will cause the material to be ignored by the search engine gods. By having two nearly identical pages, both sites can suffer in the rankings dept.
Meta Keywords are an an invisible list of keywords (usually less than 10) that are coded into your website. The search engines see them, but visitors do not. In the earlier days of search engines, these had a lot to do with ranking. They have been so badly abused, that it gets a bit more complicated now. They don't have the impact they once did, but are still part of the overall picture. Search engines have adopted logical formulas to determine natural positioning, and they look at a number of factors.
Meta Keywords alone have VERY little bearing on results. (much less than they used to). What matters is how those keywords compliment the text on the site, the title tag, the alt image tags, the url, etc. They should all work in unison, and there are tools out there to analyze this. ie: The keywords should accurately reflect the content of the page they are assigned to, and should be unique for each page on your site.
These are just my own opinions, based on personal experience. If you ask 10 people about SEO, you'll probably get 8 different conflicting answers
There is some good info about this topic in the "Experiment" thread.
Mike