Another "weird trick" sites use is to include numbers in headlines. The sidebar of this very Slate article lists headlines for "7 of John Adams' greatest insults" and "'A Different World': 12 Things We Learned". There must some psychological lure that makes readers think "oh, that is such a specific number that it must be a very important and definitive list!" :\
Note that it's not numbers per-se, it is a list of things (with the length of the list identified, and often a 'top' list.) This is a well known method to drive hits in blogging.
