The adept use of social media is clearly becoming important, particularly for young scientists. Apart from the obvious pleasures of not only reading what other people write but having a personal voice, science outreach is (at least theoretically) a factor in funding applications (e.g. Marie Curie), salary negotiations (at least at our Aalto University), and as far as I've understood, possibly even in tenure decisions. To me this seems eminently rational: the public are the ones paying for our research, so any increase in their direct access to researchers and information is not just a good thing, but the right thing. Having a visible (and measurable) presence in the social media, the blogosphere, and giving presentations popularizing science are good ways to demonstrate one's commitment to outreach. Personally I think Google+ clearly shines in this regard. The trick is to follow and get into circles devoted to science – my G+ feed is awash in more interesting science than I have time to follow, and I've managed to garner close to 4000 followers. Not a ghost town by any means for those passionate about science, it's just that it is completely different from Facebook. I also love how one can interact directly with rather prominent scientists and bloggers in a way that feels meaningful.
Starting a blog was the logical next step, and so far feels like a very good decision. I do hope my readers agree :-)
I've listed below some resources I've come across on guidelines and tips for scientists interested in honing their skills in the use of social media. If you know other good ones, please chime in the comments!
Edit: a great recent article in PLoS Biology: An Introduction to Social Media for Scientists