I did a little research on this, and the opinion of web designers seems to be that nofollow has come to be intended to mark sites are a direct competitor to you, or to non-editorial content (e.g., links submitted by users).
One would think that mostly a social link is a link to your own social media, and it seems pretty universally agreed that linking to other content that is really your own is a good idea. You are not promoting Facebook, you are promoting yourself.
Said another way, links from your site can be used to evaluate the quality of your site – “good” links help, and links to your own social site are mostly considered as good links that indicate better quality for your own site.
Thank you for answering, and I think you have a reason.
But there is this thing called “link juice” and I don’t think I want to waste it for Twitter profile, or FeedBurner page. It’s just a profile I don’t care about. I would rather focus on the site PR. Btw, as a minor detail, links from FeedBurner to my site are nofollowed, the same for Fb.
I already have a Fb LikeBox iframe which maybe is followed by Google Bot. The small social Fb icon is displayed in menus only on phones and smalltablets, and would be the second. Does this imply more “link juice” that is lost ?
I don’t know much about it, but maybe it would be useful an easy option, so admins can choose what they need for every specific link.