All mine have a fairly well hidden identification in them. By declaring I had done it, I did get a decent insurance discount.

This is really about marketing though, and if Martin can sell more by having Ed Sheeran or Eric Clapton's signature, that is a business model.

A jazz musician I did some work with a long time ago always played Yamaha any instrument he played. Not because of quality, value, ease of use or sound, but because his session and backing band work didn't pay too well and Yamaha kept him going in instruments in return for his photo on the odd advert and the occasional shop session at their stockists.