See this article:-
http://cameraergonomics.blogspot.com/2012/09/micro-43-shutter-shock-revisited-omd-em.html
(Newly discovered website introduced by the 1001 Noisy Cameras.)
Well, we all know, DSLRs have mirror slap as well as the shutter movement that cause camera shakes right before the exposure and hence image blur. But then mirrorlesses have yet another shutter movement in lieu of the mirror slap, so the final results obtained could not be better! :-o
Btw, Sony has its electronic first curtain shutter by now in their latest NEX and A series bodies, I think it will decrease the shake effect and should improve shutter lag. However, the side-effect of it in particular to any possible impact on the IQ is yet unknown, if any. (I do not believe that it could be a perfect design, as for most of the time everything is just a trade-off!)
Previous Related (Latest First):-
A 5000 fps Video Showing Mirror and Shutter Vibrations of a DSLR (The High-speed Nikon D3)
K-5 Mirror Slap Blur Issue
K-5 Shutter Blur Effect Tested: K-5 is Half of That of the K-7, Told Lumo
The K-x Blur Issue