Is there a difference in commercial, charter 'secrets' and between a couple of amatuers that share the same waters?
Obviously the consensus is that if you find a spot in the middle of the ocean and bring clients there for income, there should be a signed agreement that GPS is not allowed. For all the captain knows, you're selling or sharing info with his competition or allowing others to put pressure on the spot he paid for dearly.
On the other hand, would you share with strangers, the secrets that you or your friends paid dearly to discover? Even if the body of water is many miles long and over 100' deep, you can't assume that the 'word' won't spread as to exact locations and lures. Fish are said to be in only 15% of a lake's area. Those areas may only be in a few locations, but with half or more, pressured by locals.
When it comes to fishing, few of the best local anglers share info except with persons who have an equal amount or valid info to share and that can be trusted not to blab all over the place.
If someone follows my boat as I'm catching fish, I scoot out of there and answer no questions. If that person wants to know more of what, where and how to catch fish, let him join a local club and pay his dues like I did. I may be very selfish, but experience tells me that anglers are selfish and that some are very irresponsible when it comes to gifts.
I'll discuss general info anytime, with anyone, over a few beers, but don't ask me where my spots are!
Frank M