No, just read the guidlines here: http://static.googleusercontent.com/external_content/untrusted_dlcp/www.google.com/en//webmasters/docs/search-engine-optimization-starter-guide.pdf
That document only tells you how TO use nofollow, it does not say you should make everything dofollow. lol
My opinion is using some no follows is good for its purpose. Recommending a site , but not giving the link juice. As maybe they do the same for your backlink. Most people wanting a good value link exchange will ask you to remove the no follow on their link.
Nofollow and Dofollow links have nothing to do with the rankings or placement ofyour site. Both are links and both have clickable value. The major difference is the sharing of the PR. A link that has a Dofollow attribute will share your PR to where it is linking to and hence your link juice will be diluted. This will make it difficult for your site to raise its own PR. If you have a Nofollow link, the link juice will not be shared and hence it will be easy for your site to raise its PR. Provided ofcourse you have quality high PR Dofollow links coming to your site.
No-follow does pass a little benefit but its not have as much as do-follows. so we should be careful to choose Do-follow links.