It's one small step for artificial life...
Memes are viruses. :) I mean this as a technical distinction, not a judgemental one: they fit the definition of a virus within the LJ community. Quizzes and surveys are memes, too.
(Unlike a worm, a virus cannot spread without assistance. It is propagated by vectors such as humans trading programs with their friends (see sex). The virus may do nothing but propagate itself. Usually, however, after propagating silently for a while, it starts doing things like displaying "cute" messages, and may do irreversible damage, like waste inordinate amounts of brain activity or solicit money for crush results.
meme - /meem/ n. [coined by analogy with `gene', by Richard Dawkins] An idea considered as a replicator, esp. with the connotation that memes parasitize people into propagating them much as viruses do. Used esp. in the phrase `meme complex' denoting a group of mutually supporting memes that form an organized belief system, such as a religion. This lexicon is an (epidemiological) vector of the `hacker subculture' meme complex; each entry might be considered a meme. However, `meme' is often misused to mean `meme complex'. Use of the term connotes acceptance of the idea that in humans (and presumably other tool- and language-using sophonts) cultural evolution by selection of adaptive ideas has superseded biological evolution by selection of hereditary traits. Hackers find this idea congenial for tolerably obvious reasons.
~partially stolen from dictionaries)