clipped from: lorelle.wordpress.com   
when I do a search on a WordPress blog, or visit the categories, archives, or any other multi-post pages, I’m intent on finding what I want, not reading through every post that may or may not apply. I’m on a quest, so I want information fast.

I believe excerpts, especially in search results, helps the reader get to the information they need faster, making them happier readers, thus I’m in favor of using excerpts on multi-post pages in all WordPress Themes, not full content views.

WordPress makes changing your content displays on your own full version WordPress easy. To change the way your content displays on these pages, edit the appropriate template files with the built-in Theme Editor (Presentation > Theme Editor) or any text editor and search for the_content() and change it to the_excerpt(). That’s it.