The no-follow on widgets is understandable. The no-follow on infographics is less apparent but also understandable. The reason is because the citation is not a vote for the site linked in the infographics credit.
A true citation is when a publisher gives a citation/link to your site because they think it is relevant/useful for a specific topic or product.
We discussed in 2009 [webmasterworld.com] why viral link strategies were not a long term strategy. And last year [webmasterworld.com] we discussed why infographics were not a long term strategy for much the same reasons why viral links were not viable.
Aside from build something good and tell others about it, indirect strategies also work well because they encourage actual citations.