The know-it-all friend (KIAF).  I had a customer who spent a great deal of time with me and had visited other stores before coming to DC.  She decided to purchase on her second visit.  She was happy with our prices and our service.  My parting advice to her was to be happy and not to research further after she had reached home, simply because I wanted her not to worry about this part of her new build anymore.  She took my advice, well that is until her know-it-all friends had arrived and told her that she had been ripped off.  I asked my client if her friends had any experience in audio visual, to which the reply was a "no".  
 
 
 
The problem is not with my client, but with these so called friends with no understanding of social etiquette.  Even if she had been "ripped of" (which she clearly had not).  Does one really enter one's friends newly built house and proceed to tell them they did not make right decisions or they have been ripped off?  
 
We welcome KIAFs into our store, but please remember that we are well trained in what we do,  it makes no sense at all to rip off a customer.  Word of mouth is our LARGEST form of advertising.  You would not take a KIAF with you to the doctor with you and then have him/her argue with the doctor because KIAF does not agree with the prescription or diagnosis.  Similarly when KIAF tells you that you have made the wrong decision, please understand the unsolicited advice is usually more about the needs and inadequacies of the KIAF as opposed toyou.
 
Before you offer advice to someone try to figure out if they actually want it.