[karamazov]

It all depends on what you view with the Internet, just like the quality of a life spent with books depends on exactly what books you're reading. If all you read is romance novels, you won't be stimulating yourself adequately; the same is true online. If you choose to access only brief news articles and simulator entries, for example, you may learn a lot; but you won't stretch your mind.

Every now and again read something difficult; something that makes you think and leaves you confused. You'll learn more in the long run. A great place start, if you happen to be interested in math, is Terence Tao's blog, and a number of the blogs he links to. (At the least, I find it challenging; the blog is over at http://terrytao.wordpress.com/ .)

[gruseom]

This is the sort of platitude that it's comfortable for everybody to agree on: it's just the quality of the material that matters, so just read better stuff. Well, no. That isn't the only thing that matters. The medium also has an effect. The internet is an excellent medium for random access to specific things and a poor medium for substantial thought and reflection. It's a mile wide and an inch deep.

Tao's blog is excellent, but how does one acquire the background necessary to understand his mathematical posts? By rolling up one's sleeves and doing hard work, most of which is likely done away from the internet. And this is the kind of thing that spending a lot of time on the internet makes it harder to do. That's my experience, anyway, as well as my observation of others'.