[gtirloni]

1. When people come unprepared to discuss the meeting's topic and all the meeting is wasted bringing people to the same level of understanding (e.g. discuss CI options and some people don't know what CI is, made up example). As a bonus, the people that got their day disrupted because they have to prepare for the meeting feel frustrated that others didn't do the same.

2. Vague meeting goals and no expected outcome. After an hour, the meeting ends and nothing was decided, no clear consensus, etc.

3. Having to join a meeting because people can't communicate in written form properly and think a meeting will be easier. Especially hard when people are in different timezones.