Why is so much Internet content recycled?

The more time you spend on the Internet the more you discover that Internet content is almost 80% recycled.

Before you call me a hypocrite, yes I know that I feature best-of lists and talk about things that have been discussed before. So why am I bring this up? Because StumbleUpon, Twitter and other social services seem to make this problem worse not better.

For the third time I have found StumbleUpon saying that I have reached the end of its suggestions for me. Is this a sign of Stumbling too much, or being too picky in what I like? More importantly is there better things I can do with my time then looking at recycled content? I think yes.