Yea, some of you are right. MSD means nothing. You didn't have to do anything to get it. You didn't have to demonstrate any kind of skill, take any training, do any kind of rescue work, etc. Just a crappy piece of plastic.
To some it means something to some it doesn't. I got mine becasue I didn't want to pay $36 to get either my AOW or OW with my EANx on it since I had already paid for those cards. I figured I would pay for the one new card so that I could have a card that showed BOTH that I was certified to dive, certified to dive AOW dives and certified rescue and certified to dive EANx. This way I only have to remember one number ever and only have to show one card for any dive I want to do on a recreational boat or dive shop. Easy Peasy. It was convienience for me. That way they DMs at least have an idea that they don't have to babysit me and can wander off to the tourists.
If I get on a tech charter then I simply show my NAUI Trimix II and I am good for pretty much anything there.
As far as signing other's logs, some agencies don't even use numbers. My NAUI cards only have my name, my instructors name, and his number.
As actually meaning anything "TRULY". It doesn't mean anything just like any other card from any and all agencies. What actually means something is the attitude that the individual takes and if they actually learn how to dive and can perform the tasks they are trained to do. It actually matters if they continue to learn, put what they learn into practice and actually practice what they learn. It matters if they can actually function as an effective team member (if I am diving with them as my buddy) and not panic if something goes wrong with either of us. All of these things I learn from a diver by diving with them. I will simply not go on some dives with somebody till I have tested them myself through actually diving with them and learning how they handle situations we come across and by actually talking to them. Hopefully they are doing the same to me.
As far as continuing to learn, I don't mean paid training alone. I have learned soooo much from just diving. There are so many other sources of learning beyond actual agency training.
So, in the end, I guess really MSD card doesn't mean anything, but neither does the OW, AOW, rescue, ______specialty, instructor, etc. I have seen some awesome divers that had nothing beyond OW and/or AOW and I have seen some crappy divers that have 10-15 certs from OW through technichal training and quite frankly they suck simply because their attitude is crap. They cannot dive as an effective member on any kind of dive and take uneccessary risks because they fail to properly apply the triaining they recieved.