I came across this article today and wanted to pass it along. I've noticed a substantial increase the number of articles, studies, and general commentary on the adverse effects of multi-tasking. Here's another one that provides some additional evidence and insight. It's a very quick read, well-worth the time, but first finish what you're doing so you don't multi-task yourself!
http://www.linkedin.com/today/post/article/20131003165549-128811924-why-focus-should-really-be-the-next-big-thing