If the inspector is not careful, or is too rushed, he may miss some things.  Some missed items are not a big deal while others are a major issue.

In this picture, another inspector missed this completely.  This is an extension cord wire connected to a ROMEX NM wire with the connection wrapped with duct tape.  It is sitting on top of the metal HVAC cabinet in the attic at the top of the pull down stairs.

Be sure when you hire an inspector, hire the right one.  My inspections last over 2 1/2 hours.  I check all plugs, switches, windows, doors, etc.  I am not rushed to get to my 6th inspection for the day.