Let me quickly defend the Wikipedia here: Yes, the deletionists are annoying. However, there is a reason why "non-notable" articles are deleted: To minimize the number of articles that have to be watched to make sure spammers and vandals don't damage the articles.
Every time someone makes an article, that's one more article admins have to baby-sit. Even with thousands of people looking for spam and vandalism, there's a lot of subtle vandalism that gets in under the radar.
If every single high school or every single garage band or every single webcomic had a Wikipedia article, it would strain the admins ever more.
It's amazing that admins are able to keep the vandalism under control as much as they have been able to. Wikipedia is an Alexa top 10 site (I can't say the same for Slashdot, not by a long margin), and its purpose is to provide useful information for readers. Which is does very well. Yes, the Wiki is imperfect, and, yes, it has admins who have power trips, but the system works.