MHes - 5:38 pm on Dec 12, 2012 (gmt 0)
Just looked at Matt Cutts blog for 2009 and he says "Nofollow links definitely donít pass PageRank....The essential thing you need to know is that nofollow links donít help sites rank higher in Googleís search results."
hmmmm... I think it can help by avoiding you vouching for a dodgy website by mistake. If you put nofollow, you are basically saying you don't vouch for the website you link to, which is stopping you being caught linking to a bad neighbourhood.
Matt basically says its smart to add nofollow some of the time... as TheMadScientist said.