Here is a nice video that explains on what we need to do in terms of link Building, is it footer links or in content links ? Well the video stated that in content links is better than footer and it gives better trust.
The video by Matt Cutts [ Google Engineer ] explains that in the long run it will be better to have an authority link by having a incoming links from post. So I think it would be better to have a link post exchange links rather than side bar blog roll links.
In my opinion this is better for the long run SEO tactics, But for the Current Events SEO tactics , I think Footer and blog roll links is better. But of course Matt is the Google Engineer and not me 🙂