Vendor term used to describe a customer who is implementing a technology or product as well being able & willing to publicly discuss that.
Of course, you won’t hear about “lighthouse” customers if the technology fails (happens sometimes). What few people know is that lighthouse customers receive high levels of support form the vendor to ensure that their public statements are glowing, positive and full of happy joy.
Few companies are willing to talk about their experiences – IT is competitive advantage, and why bother wasting time on pointless promotion. Therefore, most references come from companies that like pointless promotion – like universities, media companies and government entities.