I just got bitten by a problem in AWS CLI where S3 files won't sync when you expect them to:  got me thinking. What are the major unexpected behaviors, or "gotchas", exist in the software you use?Where do you see the "Principle of Least Astonishment" violated?  think we may all benefit from sharing with each other. Hopefully it'll save some of us from being bitten by odd software behavior.I'm referring to tools, programming languages, database and server software, etc.  I think it would be really useful to raise awareness of these issues.