How do you know if pairs are not working?

1. If one person in staring at the monitor while the other keeps typing for more than 15 minutes.
2. When a pair starts to become a mini gang. It two members get along well and start pairing they do well, bringing the other pairs down.
3. When pairs are stuck in the same task for ever and start doing other things during thier time
4. Its easy for the pair to lose focus just as one person, if they dont know the ettiquettes of pair programming
5. If one of the pair members is forced to pair.