I haven't "been there or done that", but the last time I encountered an experienced So. Pacific sailor he insisted that I accept a thumb drive full of tracks into and out of Pacific atolls and anchorages. Apparently, swapping tracks is very common in areas where charts aren't that accurate. Following someone's GPS crumb trail is apparently safer than trying to navigate on a chart where the longitude is several miles off. In areas of the world with accurate chart datum swapping tracks is, in my experience, much less common.
The method for up/down loading tracks into or out of the thumb drive is above my pay grade.
Just saw that not only can we save our tracks but we can collect sonar data during the whole track and then upload it to maps to be included in the Navionics maps. It's seriously amazing what technology can do now. How to record sonar logs with Raymarine | Navionics
Crowdsourcing data collection like this is a really great idea. You're sailing/motoring over it anyway, and it's not really a big deal to collect the data, so why not? The beauty is that it doesn't require any one person to track back-and-forth over an area. With the chaotic nature of people's travel on the water, and with enough participants, you can get a really good idea of what many of the popular areas look like, and how they change over time.
It's similar in some ways to the way Apple and Google use cell phones to collect traffic data. They know where you are and how quickly you're moving, and with hundreds or thousands of others around you also providing data, they are able to quickly determine whether your data is an anomaly or not, they can start identifying good bail-out routes for those using their mapping systems, etc.