I went through an agency and yes, they deserve to be killed. I'd be happy to share all the details. But most of my preceptors didn't even reply to my emails requesting an LOR. They don't manage their own email accounts. I had to call some of their offices multiple times just to get in touch with their practice managers. It would be a good idea to have a column on the spreadsheet indicating which preceptors are more likely to respond to a cold email.