I spotted this on Digg, I think some more testing needs to be completed with better control groups, files and players but even if there's a tiny loss, that's a huge waste of time and power - "Tests were done on portable music players using standard MP3 files and DRM encrypted WMA files. The results. Up to 25% less battery life thanks to DRM sucking the juices as it constantly verifies licenses." - [via] Link.
Between Sony's rootkit and a potential 25% loss of battery life, the music folks along with the hardware & software vendors and really accelerating a customer revolt.
Pictured here, vintage batteries from AntiqueRadio.org.
http://blog.makezine.com/archive/2006/03/drm_shortens_player_batte.html