Just like in any other profession, there are good practitioners and some not so good. When choosing a home inspector, make sure you get one with some industry experience. Here in Georgia anyone can become an inspector. There are no licensing or testing requirements to become an inspector.
A recent inspection of a home I had listed turned up a supposedly malfunctioning ceiling fan. I was a bit perplexed because I had just had the fan on the week before and it worked just fine. When checked yesterday it was still working just fine. I guess the inspector was not well versed in fan operations.
When you hire a home inspector, make sure they are ASHI certified. While this will not cull out all bad inspectors, it will show that the inspector is serious about his chosen profession. When looking, ask around as well. Your agent might have some great recommendations for you or check with a recent home buyer to see how they liked their inspector. It is just too important for a buyer to not hire a bad inspector.