Most riders do at least the bare minimum to assure their bike is safe. Things like checking the fluids, tire pressure, chain tension etc. The most overlooked aspect of safety on a motorcycle is proper suspension setup. Any bike with adjustable suspension needs to be setup and maintained for the bike to handle properly. If you are running the wrong spring rates/air pressure and/or improper spring preload the bike will become unpredictable and will not perform as expected. This can cause the bike to become unstable and experience head shake at high speeds or it may steer poorly and wash out easily. Either way, you need to make sure your bike is setup for your weight and make sure to check your sag like you would check the air in your tires. To take the necessary measurements you can get a freind and a tape measure, or you can use a purpose built system like the Slacker Digital Suspension Tuner by Motool.
It is easy to overlook little changes over time that add up to a poor handling bike. Little tweaks as the chain stretches out, changing tire or sprocket sizes, changes if your gear or weight as well as suspension wear all add up over time. The good thing is you will catch it before it gets out of control if you check your sag regularly. A good example was when I changed rear sprockets and the axle moved forward in the stays about 25mm as a result. This caused there to be less leverage on the swing arm so I had to loosen the spring a bit to get back to where I like it. My rule is that whenever my handling seems off I check the sag before anything else. I also check it any time I change tires, chain and sprockets, especially if you are changing sizes. You would be amazed how much moving the axle will affect the bikes handling. You bike will be safer and more fun to ride so you can push it as hard as you desire.
With the popularity of ADV and Sport Touring bikes it is even more important since the load is always changing depending on what you are carrying or who you are carrying. If you are going on a long ride with a passenger, you should set the bike up for both riders or you will find the bike very difficult to steer and you will likely end up washing out or blowing a turn all together. Always consider what load you are going to have and set your sag accordingly. Not only will your bike be safer, it will also be a lot more fun to ride!