If your boyfriend / girlfriend kissed somebody else, what would you do ?

I would end it before I got hurt!

It would depend on how did he kiss her
Why did he kiss her... etc...

Two extreme opposite examples

Like she is an old friend and they saw each other for the first time in a long time... I can understand

He kisses her because she is sitting there looking cute and he just has the urge...
Bye bye boyfriend!

Depends on why she kissed them.

Again depends on the situation.

Kiss them, too. Sauce for the goose and all that.

In Hawaii, people hug and kiss all the time as a greeting. So unless the kiss occurs outside of the hi, or goodbye, it isn't obvious if there's something else going on.

Depends, if it's a lip lock kiss, I exit stage left.

If it's a greeting on the cheek, then I just go along with it. If it is someone that makes me uncomfortable, then I bring it up later on when we can discuss it calmly