First, the engines expect to see a balance of "no follow" and "do follow" links. And while there's no known ideal ratio, devoting all of a site's link building efforts to finding "do follow" links would be a misuse of the agency's time.
There has also been no conclusive proof that the Big Three engines aren't passing some PageRank through "no followed" links. And focusing on link juice itself actually eschews the real value of links--the increase in traffic they provide.
"Focus on getting links for traffic and you won't have to worry about it at all," the team says. "So much emphasis is placed on getting link juice for search engine rankings that many forget that the best links of all bring real traffic to your site."