1 article in multiple categories. duplicate content?

Hey guys!

ive tried to find the matching section for this question, this was the closest (i think)

So i have an article directory site, problem is, people make 1 article, and select more then one category for the artcile, and i usually agree with them on the choices, some articles can fit in 2 or even 4 categories at once.
they only made 1 article, and then selected, lets say 4 categories for it, will i get punished by google and other search engines for duplicate content, even tho its only 1 article?

am i making sense?.. i feel like a newbie now, but hope someone can clear this up for me.

No, having several URLs with the same content will not be penalized. Only one URL will rank though.

Read this for a full explanation:
http://www.blackhatworld.com/blackh...0259-guide-duplicate-content-myths-facts.html

great info you got there, been digging thru alot of websites trying to find out.

although i dont see a benefit of posting 1 article in several categories if i want to build a good and proper directory over time. (am i cheating myself out of ranking etc then ?)

SEO urls also can represent this. Wordpress uses "canonical url" to get over this issue.

i have tried several WP themes for article directories, and they always contain an option to prevent people for posting in multiple categories with an explanation that it will "prevent duplicated content"
as i see it, they only mean duplicated content on the website itself in form of same article in more then one place, not duplicated content search engines penalize you for?

after reading L Brown`s provided li*k in his post, i understand it so that SE does not penalize duplicate content on your own site, only if they match other peoples sites that have had the article indexed/published longer then your site. im getting confused

i now realized that my title should have been "should i let people publish their articles in more then 1 category/subcategory?" ..hehe