While filling out a logbook is completely optional, divers should be aware that many resorts and dive operators will ask to see your logbook before allowing you to come on a dive that requires anything more than basic open-water "just been certified" skills. On my trip to the Florida Keys last spring, a buddy of mine who was far more experienced was almost not allowed to dive: up until then, he had never logged his dives. He didn't see the point. If a very experienced Dive Master and I had not been there, both of us very particular about thorough logging and both vouching for his experience, he would have been left on the dock. Needless to say, my buddy is now as religious about logging as we are! Imagine spending all that time and money travelling to your vacation destination (we had driven from Texas), only to be told to wait in the hotel room...
Also, you need to know that in the case of a diving/maritime accident or lawsuit, the logbooks of any divers in the area of the incident are subpoena-able documents. Having lied in your description could cause a miscarriage of justice. Altering logs after they are subpoenad is a crime - for which Martha Stewart got to make some new friends at Camp Cupcake recently (she altered her phone logs after they had been subpoenad).
The best part, though, is reading back through your logs and remembering the people and places that you have been.
also a great way to keep track of how your reducing the weight you need and how much weight with what exposure suit. I dont know why someone would make fake entrys tho, I havent logged about 1/3 of my dives as they were just practice or short dives. It would be only hurting oneself to fudge the log book as its there to help you.
