What you raise, is what has been my concern.
We are in a competitive market fighting it out with a lot of sites with similar focus and similar offering, so cross-domain duplicate/near-duplicate content ends up being the main focus for how we optimise this area of our content.
This no-follow thing has just been in the back of my mind as something I should look into just in case we are giving out a negative signal in someway.
And in our case, it is not the link that is paid for. They are paying to post a job vacancy - the link is mechanism for applying or finding out more.
So how does a search engine detect what is paid for and what is not?
This is my first SEOmoz question, so I am really excited to have two people respond so quickly... how wonderful the community here!