Well we know that many people write an articles on we buy it but many people buy PLR articles and many user used it on their websites. Is there any problems to have same article on many websites?

 I think if Google found same topic on many web pages than they will not indexed your pages and also they penalize your sites and that's not good for your websi te.

Well if Google will not count it  and they will not indexed pages than why poeple selling PLR articles and buying it. I seen many places where people selling it.

A lot of people are even relying on article rewriter software's but as mentioned by Weblove, Google will penalize your site if they find out you just copied it. It's still best to be original.