Matt Cutts answer to: Should I add rel=“nofollow” to links that are included with my widget?

Matt Cutts in his recent podcast on Google webmaster channel on Youtube said using widgets and infographics to gather links is not a good practice, and one should avoid such practices especially if they are using a widget. Matt Cutts explains that people just copy and paste widget codes without even realizing that there are hidden links under the hood.
Matt Cutts in nutshell said he would recommend to add a rel=“nofollow” attribute to widget links, as they are not the preferred once in comparison to editorial links.

What should we do with embeddable codes in things like widgets and infographics? Should we include the rel=”nofollow” by default? Advert the user that the code includes a link and give him the option of not including it?
Christian Oliveira, Madrid