Before purchasing anything from them, I asked them to send me references of their sales of equipment to various customers that have dealt with them.. I wanted to take it upon myself to contact customers personally to see what their response has been! They have yet to return an email to me.
When buying large dollar amounts, that is reasonable, as in way more than a couple of US$100K worth, then sure customer reference is reasonable. in the IT world, I was involved in multi-million dollar purchases, and such calls are common place. And customers agree in advance to participate in such calls
Individual small customer... no... you could be a competitor fishing for leads, not to mention you are requesting they violate their privacy agreement which prevents sharing contact info, etc.
sorry, yours is an unreasonable request... and a polite, we can't/won't do that would be reasonable, but they could just as easily assume your request is not legit (personally, I'd be wondering if 'under the influence' or neuro-atypical), and ignoring you is their best course of action. no idea, and if company overwhelmed as other responses indicate, probably not worth their time to respond
And even in the completely unrealistic situation where you did get such a customer list, you then run into sampling size considerations, and cost/benefit of contacting hundreds to get to a decent confidence level (basic statistics)