Wikipedia is the best example of what the 'wisdom of crowds' can achieve, although it is not without its detractors. To get an overview of the pros and cons, read the Wikipedia page about Wikipedia itself, and some of the pages linked to from it.

Next, explore Wikipedia yourself - look up some things that interest you and see what Wikipedia says. Look at the references linked at the bottom of the page - whatever the merits of the Wikipedia article itself, it can be a good starting point for research elsewhere on the web.

If it's something you know a lot about, does the Wikipedia entry seem comprehensive and accurate to you? Have a go at editing the page if not! For the vast majority of pages you do not need to sign up for a Wikipedia account in order to edit.

Take a look at the 'history' and 'discussion' tabs for the article (at the very top). These can make very interesting reading, particularly for controversial articles or subjects where there are strong opposing viewpoints, as you can see how the current version (and consensus) has been reached. If you make a page edit, return to the page a few days or weeks later to see if your edit is still there, and if not, check the discussion and history tabs to find out why not. You can, of course, always argue your point and make the edit again.

And finally... write a post on your blog with your thoughts (tag it 'Thing 18')