I fly a decent amount (12-20 times per year) including international at least once per year and have for the past 15+ years. Never have been bumped nor remember my seat being changed. I hear all these stories, but wonder who it is happening to. I hear them asking for people to change flights all the time because of being overbooked, but I never heard them literally not letting the person on the plane that had bought a ticket. Somebody always ends up taking the voucher. Highest I ever saw it get to was two full airfares with no restrictions and they needed two people, one guy got up and then nobody else and I thought they were going to say three tickets at which point I was getting up but somebody then got up and took the second after about a 15 second waiting period. And there is many times where I don't get a seat assignment when I check in because obviously they are overbooked but I just goto the counter at the gate and they give me a seat.
I actually think that generally the airlines now are much better than 10-15 years ago. I don't have actual statistics, but the amount of time my flights are delayed (weather doesn't count) or they do circles of the airport for 30-45 minutes waiting to land seems much, much less than it used to be. Flying unless you are platinum or greater status stinks. There are lines and planes are crowded and things get delayed, etc...and you have little to no rights. But if you just accept that is the way it is going to be as there is not much you can do about it, then it isn't that bad. I now just make sure I always have multiple TV/Movie downloads on my IPAD and have put the Comcast App on there two as when in the airport it is simple to watch TV on your IPAD through that app. So if you have stuff to do, the the waiting becomes much more tolerable.