1) Memes Are Viral
    The first property of memes is that they're viral. For all the power and potential of the Internet, most people use it primarily for entertainment and distraction, which is why sites like Facebook and YouTube are so popular, and companies like the Cheezburger Network have built entire Internet empires from funny pictures and videos. Memes are ideal fodder for entertainment on the web because they're quick and easy to consume, which is crucial given how short people's attention spans are.
     
    Memes are also typically humorous in nature, and people love sharing a good joke. Just look at your uncle who always mass-emails jokes to his entire contact list, or your friends spreading the latest "What People Think I Do" pictures on Facebook. People like being entertained, and if they find something particularly entertaining, they'll pass it along to their friends, who in-turn pass it on to their friends, and so-on and so-forth. That's how content goes viral.