I get this when I do a :site search on my forum. The thing is None of the pages on my forum are similiar, all topics have lots of text in them in forms of celeb biographies, all subjects are different, all meta keywords and descriptions are different as well. Im worried that they have ommitted them as they see them as duplicate content (What other reason is there) and thus will penalise me but as I say NONE of the topics are similiar.
Cant give it out as its adult related site, but all the info is there in terms of what could cause a problem.
This is perfectly normal - in order to return results as quickly as possible they list the pages that are the most unique for that site. Based on your OP, even though each page is different, they all follow a fairly broad theme so they serve up a "Sampling" of what's on the site. If they didn't do it that way, serving up tens of thousands of pages on large sites would bog down the available resources and slow things down considerably.