Any time the main character acts in an untypically stupid fashion, such as not raising the shields when they should, or trusting an obviously untrustworthy type, in order to develop a situation where the character must now act heroically to extract themselves and others from the situation of their own making.
To this author a lame method of setting up the situation or advancing the plot by having your protagonist act in an untypical manner, so sloppy plot development can occur. Captain Kirk not raising the shields in Star Trek 2 is a perfect example. To be avoided in any case. (Sandi Hedlund, Garry Stahl)