---Attrib. Stanislaw Lem.
Bjarneskans, Grønnevik and Sandberg (2000) state that: Memes do not only influence behaviour to promote replication, but many of the most successful memes have other side-effects (for example, being able to invoke various emotions) or promote their replication by being useful or through other features (like parasiting on other memes, e.g. parodies and imitations); using a biological analogy one could say symbiotic memes spread mainly using their usefulness, while parasitic memes compel the host to spread them. This compulsion can be more or less subtle, ranging from explicit orders like in chain letters ("Send ten copies of this letter to your friends") to implicit influences that link with our attitudes like the "Save the whales" meme described in (Hofstadter 1985, p. 55).
It is quite common that memes are confused with ideas/thoughts. Both are cognitive structures, but an idea is not self-replicating and is spread passively (i.e. for extrinsic reasons) if it is spread beyond its initial host at all. The difference is sometimes hazy; the idea "Isn't it time for us to eat?" can easily spread in a small group, but will not spread well outside the group and will disappear once the question is settled, while a meme usually can spread generally and does not have any limited lifespan. Taken from: www.aleph.se/Trans/Cultural/Memetics/memecycle.html
Memes are virul, they are non genetic replicators and can spread like wild fire. I have found it difficult to refine the Meme to a definitive meaning and the above extract helps clarify that Memes are not simply ideas or stories that are spread between small groups of friends. It's good to know what they are not; in order to grasp what they are....