I don't think they devalue the links because the search engines want to see you active in social networks. One that is active in social networks is clearly trying to build their business. It is a good reflection in the eyes of the search engines. At the end of the day you want a well diversified group of links.
the search engines want to see you active in social network
I call speculation. There's no evidence to support this, and I would suggest there's plenty of businesses that have literally no use for social media.
Volvo's - this should be a topic of tweets and facebook? Annuities? Road paving equipment? etc. etc. If you're in those markets and are tweeting, I'd say you're pushing the spam envelope, not much different than autosubmitting to directories in terms of quality.
Not that I have an opinion on the OP, but suggesting teh SE's have a preference that businesses jump into social media, I'm not so sure.