Once again, we have a lot of disagreement going on about what makes an Internet Meme, and people requesting a definition. Here's my view. Feel free to ask questions, or correct me where you think I'm wrong.
What is a meme?
A meme is any relatively popular idea that spreads primarily from one person to another in what appears to be a contagious fashion. A strong meme is a meme that has a strong impact and influence on the cultural group in which it is found.
Examples include:
Religions, clothing styles, musical genres, colloquialisms, idioms, other parts of speech, philosophies, popular scientific hypotheses, architectural trends, and much, much more.
Memetics is, at its simplest, an approach to cultural analysis that treats cultural information as though it acts in much the same way as biological information, or DNA. All of the genes present in the DNA make up the physical aspects of a person, just as all of the memes present in a cultural group, make up that culture.
What is an Internet meme?
An Internet meme is a type of meme which is more relevant in the context of Internet communities and their cultures than it is in any other media.
Examples include:
Advice Dog, All Your Base Are Belong to Us, Demotivational Posters, and much more.
<Note: Kanye West's VMA interruption is a meme that had plenty of mainstream exposure. But the "Imma Let You Finish" recontextualizations happened online, and have more relevence to Internet culture than they do elsewhere.