Yes, I find it very annoying-around here there are a lot of fishing boats that could use AIS enroute to their fishing grounds, or in fog - all transponders have a silent mode you could turn on to hide your location (presumably to hide from pirates). We frequently talk to large ships, and yachts in the confined areas downeast - once you see a ship's name on the AIS and hail them by name, they always answer - whereas in the old days we'd see a large ship on radar and hail them to discuss crossing they'd ignore you - now they seek us out to let us know they see us and don't want us to cross their bow - or they've got a barge in tow, please keep clear astern... We've talked to large yachts in the very circuitous mussel ridge channel to pick a spot to pass, agree on sharing the channel, etc. You don't need AIS, but it sure is helpful.
I've had a restricted radiotelephone operators license since I was a kid - Dave is right - read English, keep a log, and the check has to clear.
The CG certainly responds to a DSC distress call - but they may not be able to raise the caller on voice. I wasn't saying that the marina would be asked to handle the emergency - -the CG, like the EPIRB alert centers, can call the contact info to verify that it's not a false alarm. The MMSI data includes a description of your vessel - it helps to know what you're looking for before you dispatch a search party! When we forward a mayday call or get asked to assist, the first question is nature of emergency, the second is describe your vessel (followed by souls aboard and lifejackets). MMSI puts that right on the screen of the new CG radio systems - and I can't believe Rockland hasn't been upgraded - the entire east coast was done several years ago.