I wrote a previous post about Commercial Stockholm Syndrome where companies who are captured and treated bad by a vendor start to develop a loyalty to that vendor. [Here is a link to an actual description of Stockholm Syndrome].
Over the last few years I have seen many cases of a similar phenomenon. Business owners who believe that their IT staff is very good even though the IT problems that they are facing are often debilitating. I had one reprographer tell me that his e-mail had been down for 3 days and he would occasionally receive e-mail that was addressed to other people in the company. He then said, "but my It guys is working on it. He's pretty good. [pause] Well at least I think he is good."
I once had a boss who told me that when you are not educated on something and you hear someone else talking about it you assume they are really competent. It is your lack of knowledge on the subject not their actual competence that creates the perception.
There are a lot of companies who have "homegrown" IT staff that face a multitude of IT problems that could be easily solved by a more competent IT employee. This doesn't necessarily mean that the IT staff doesn't have the potential it may mean they have not received the appropriate training. Competency can be hired or developed.
Another thing to look at is certifications from an external source. One example is a MCSE (Microsoft Certified Systems Engineer).