The first time I ever played, I tamed seven Dilos (Named for the days of the week). I had just set the newest addition Saturday outside my base to be with his friends...but I didn't pay attention to his aggression level. Instead of neutral he was on aggressive. Well a Bronto spawned by my base and Saturday attacked it. This caused the Bronto to aggro and the other Dilos (who were on neutral) to attack. I lost half my thatch base my mortar and pestle, and four out of the seven Dilos (Monday, Friday, Saturday, and Wednesday). Moral of the story: Always set your dinos to neutral before doing anything. If you aren't sure they're on neutral then double check.

1 up=1 prayer for my fallen comrades