In his meetings talk, David Grady explains how co-workers steal our time and we let them because of our automatic acceptance of meeting invitations.
The speaker defines a condition called Mindless Accept Syndrome (MAS). Defined as an involuntary reflex in which a person accepts a meeting invitation without even thinking why, the common illness among office workers worldwide is turning into a global epidemic.
While common conception might be that we're powerless but to sit through badly run meetings, the meetings talk explains the cure (No MAS) is to click the tentative button the next time you get a meeting invitation without a lot of information. Instead get in touch with person who invited you. This way, people might be more thoughtful about sending invitations out. Grady notes people might change their behaviour if you change yours.