Closed captioning has been around for over 20 years in the USA, and it still intriques me as to how wrong it can be. This service was originally created to give the deaf a means to watch tv. Those who cannot hear can read along with the television. I've used close captioning many times when I've wanted to follow what's going on with a show, but I didn't want the noise. It was especially handy in college when I had to watch medical videos for one of my biology classes, but I didn't want to wake up my roommate.
Unfortunately the service still isn't perfect. The bad part is the fact that it's not always correct. I could be watching something that is supposed to say "Hi, how are you?", but instead I would be reading "Hi, are you sdfjiewoauparllll". It also still blows me away that not all cable channels have adopted closed captioning. Some channels provide captioning for certain shows and not for others. You would expect that considering the service has been around for over 20 years, closed captioning would be available on everything.
There is another great use for closed captioning. Almost every alternate language channel out there provides closed captioning for every show. A friend of mine has two children ages 5 and 7, and every day she let's her children watch cartoons, but not just any cartoons. Her children watch Spanish cartoons with English closed captioning turned on. You would be amazed at how much Spanish these children have learned.
This just goes to show that closed captioning is a valuable resource that has been around for many years. Even if it doesn't work perfectly all the time, it is still a great help to those who need it, but also provides many other additional uses.