There are many issues that can end up becoming the downfall of a relationship but jealousy has to be one of the fastest roads to a breakup.
After all, if you feel like you can't spend any time with people because your partner will feel threatened by them by for some reason, that's either going to lead to a very isolating situation or the decision that this relationship isn't with the trouble.
And while I was stunned when my mom told me that a coworker's husband saw a picture of me at the office and gave the woman the third degree about how she knew me, one recent case somehow seemed like even more of a red flag.