Is running forum on same domain a G dup content risk?

referring to an article speaking about dup content

[AjiNIMC]

I was reading the post at [webmasterworld.com...] by caveman (thanks for the post).

Summary of the post wrt to forums
Say I am running a website of widgets and I have following pages.
1) Widgets index (home page).
2) Blue Widgets (speaking about a variety of widget).
3) Red Widgets (speaking about a variety of widget).
4) 20 Blue Widget's Forum discussion (discussing about blue widgets).
5) 20 Red Widget's Forum discussion (discussing about Red widgets).

most of the pages look alike with some amount of duplicate content as it covers same product.

Problem : Google will not only drop the sub pages and forum pages with the duplicate type of content but can also drop the index page for covering similar type of content.

Discussion point: Forum members will keep asking questions about blue and red widgets increasing the similar pages count. Is this increasing the risk for index page getting dropped in SERP?

Is running forum on the same domain advisable from SE's point of view? (from customer's point of view forum reflects community support, which is very much appreciated.).

Thanks
AjiNIMC