Not to kill this otherwise illuminating argument, but most appliances use UL (Underwriter's Lab) certified components and there are standards and test for such components. (Often the Green Shirt Folks at competition have something to do with UL).
This is true of most consumer products in that there are safety standards to be followed in order to be in compliance or to rate your product relative to safety (like crash test ratings for cars). Many large companies are able to self certify and have internal labs that can perform such a test. Often not for profit organizations get together and make the standards in order to not count on the wreckless calculations of an ill-prepped engineer. For instance, most lifting apparatus have some pretty major factors of safety associated with them. A lifting harness may require a 2.3 to 4x factor of safety (depending on standard) for each atttachment point relative to the entire load. These sort of safety factors are often necessary and built from previous bad experiences. for instance, a 4 chain harness without good load distribution could actually lift most (or all) the load with 2 chains. If you used a 1.5x factor of safety relative to all 4 chains for the entire load, It might work, or it might drop a really heavy object. For further reading on chains:
http://www.liftingrigging.com/Inform...ain-safety.htm
That being said, you can do your best to build a better product and idiot proof it, but society has a way of building a better idiot.
Very cool graduation present.