Ideas are those some piece of thoughts run through our neuron network, appearing for seconds, then disappearing if we don't really grab them into a record. Whenever we record them down, they become memes.
Joi Ito, Director of MIT Media Lab, once posted a blog depicting the process a meme started from mind, then travel through blogosphere to be derived into other memes, or inspired more ideas in other readers' mind, including mine.
We can't forget the contribution of Richard Dawkins for creating the term of "meme". It's not necessary to predict how popular this term is today, the term is now leading more potential of human creations borderlessly.