I once bought a toy from an Asian salesman on the NY subway. The toy he used to demonstrate worked wonderfully, but the one I bought from him and assumed would work when I get home to take it out of the box (by which he made an ass of me) worked terribly.
A motionless toy doesn't bring much joy to anyone's heart.
Nevertheless I learned a valuable lesson that day and quickly realized why people shop at stores that have return policies.
Presume and assume nothing - it's the great transgression (Psalm 19:12-13).
Assess and inspect everything thoroughly, especially that which you pay for, intend to marry and contractually bind yourself to.
Remember people don't do what you expect, but rather what you inspect.
http://www.PaulFDavis.com/ - consumer advocate, consultant and corporate trainer
info @ PaulFDavis.com