Sgt_Kickaxe - 5:17 am on Mar 17, 2011 (gmt 0)
If you have these pages to begin with it stands to reason that Google will find them and that the pages which link to them will pass value to them. A three part remedy is in order to minimize the effects.
1) Minimize the number of such pages, if you cannot add value to them somehow.
2) Minimize the number of links to these pages.
3) Block flow as high up the chain as you can. If, for example, the only way to reach these pages is through a "user tools" page you could noindex/nofollow etc that page as well.
Another trick to ensuring that these pages have a low value and don't hog rank is to place links on them back to all the important places of your site.