i have read in matt cutts blog (top google engineer) that abusing NoFollow will NOT help you.
If it was that simple why isnt everyone doing it ?
why isnt every seo firm telling their clients to use it
why isnt all the seo sites using it ?
because the nofollow tag is for linking to sites that you dont reccommend/bad sites.
Problem is its not “natural” to only link to bad/unrecommended sites – which google can easily see
Wikipedia have only recently started to use it because of the amount of link spam and Wikipedia are a special case and are not doing it to make there serps higher and make MONEY.
but if its working for you, then you are ok – as each to there own
Anyhow theres better ways to not pass over pr/vote to affiliate sites as i have mentioned in an earlier post (about doing internal redirects)