Do we need scientific journals at social networks?

It is interesting to see, how journals are trying to increase their market visibility – Nature has becoming famous for their investment in Second Life? Just recently I received an email that JACI – the Journal of Allergy and Clinical Immunology – has now opened an account at Facebook.

At least by now, it seems that journals are misusing social networks for further marketing their results beyond the usual press releases. But do we really need that? Should I add JACI as “friend” – or isn’t a repeated Pubmed search or updated RSS feed already too much attention?