So I'm on the fence about this one. I get the fact that juice vendors need to keep trade secrets. I get they sell a unique product, but there's also something to be said about how a store handles questions and full disclosure.
I have a B&M I go to that's local. I also have a acquaintance relationship, like when you have a favorite bar and they know your name. I don't purchase any juice from them, but I do taste and try and they ask for feedback.I did ask once of the owners, and they told me the companies they purchase their flavoring from. Not the exact flavors they purchase from x company, but they use 2 or 3 vendors for flavors and 1 supplier for their nic, PV and VG. I would never ask questions like "How much x flavor from x vendor", but in full disclosure - what's really wrong with asking that question? You not asking for their "Mixology", or how much they pay. I'm also not going out and posting that "X B&M is using X vendors".
Maybe the owner felt safe telling me - I'm not sure. I didn't ask if they tell anyone else, and the owner didn't say "hey - keep this info to yourself". I have no problem recommending this shop to friends and family. The shop also understands that their juice and hardware selection isn't the "end all, you don't need to go anywhere else". They even recommend other juice companies and help source products they wouldn't normally carry and not just to me, but to all of their customers.
I think you need to weigh the information disclosure - some vendors do need to keep trade secrets and not disclose, but some will and at the end of the day - Would you trust them? Actions speak louder than words.