I think the "limitless source of information" that is the internet could be part of the problem instead of a means to increase the average user's intelligence. It is a great tool to further our collective knowledge as a species, but not so great for the individual. Why does anyone have to remember anything when they can just look it up real quick on the internet? You see it all over the internet, people asking stupid questions rather than just thinking about it for a moment.
Since internet access has become basically a de facto right in our society in the past decade, kids in schools get it ingrained in their heads over the years that what they are learning is useless when it is available just a few clicks away at anytime. I think education needs to change to get more people interested in learning. It's just a rush program.
Remember this. Now write this test. Now, no need to remember that last stuff anymore, remember this. Now write this test. Schools are underfunded and don't do enough to encourage kids to learn on their own. They just pile on more homework and tests and take away things that would actually get kids interested in learning. I don't mean we need something like that awful "no child left behind" program that is thankfully finally being replaced in the US. No, kids need to be shown more often the practical uses of what they are learning and why it is fun to learn. More experiments and hands on learning for science classes, more field trips to historical museums for history, etc.
Parenting is also a problem. A lot of parents never do anything with their kids or even monitor what they are doing. There are 10 year olds and possibly younger who are just given an xbox subscription (or possibly a runescape subscription?

) and left with that as their baby sitter.
Anyone who hasn't seen the movie "Idiocracy" might find it interesting. It deals with the subject of this topic of people in the future being a lot dumber, or how dumb people already are now depending on how you look at it.