Somewhat unsurprisingly, I think it is quite useful for academics to blog and use social media. I have been blogging here since April 2011, talking about my research and teaching, science and education policy, through to minutiae and quotes. During my career, the range of expected roles for an academic/researcher has changed significantly, with increasing focus on public engagement and engaging with policy-makers. While this has most likely expanded the metrics for how an early career academic/researcher is measured (i.e. on top of a strong research profile: publications and funding), the changing models of academic dissemination and discourse reinforces the value of academics blogging.
Thus, Alan Winfield (Professor of Electrical Engineering and Director of UWE’s Science Communication Unit) and I are running a workshop on academic blogging at Engage 2013, the National Co-ordinating Centre for Public Engagement‘s annual conference to be held in Bristol on 27th-28th November. The headline focus for this year’s event is partnerships that count; it should provide a great opportunity for open dialogue between the HE community, policy-makers and funders, and the organisations working with them.
Our session on academic blogging is on the afternoon of the first day (see the programme) — book online now!
Digital, Data & Policy 
Also worth looking at A set of top Computer Science blogs from May 2012.
Excellent article by Athene Donald in Physics Focus: Tweeting and blogging aren’t wastes of academic’s time — they can be valuable outreach
Storify of the workshop, plus interesting blog post from Steven Hill: On blogging and public engagement