In 1976, Richard Dawkins proposed that we can understand the spread of cultural entities such as ideas by analogy to biological evolution. He named such entities memes, by analogy to the genes that enable the transmission and selection of biological traits. The general attempt to model cultural developments on biological ones has been called memetics.
I think that memes and memetics are bad ideas because of the substantial differences between biological and cultural evolution. First, the lumping of all cultural entities together as memes neglects the variety and complexity of mental representations, which include concepts, images, beliefs, emotions, and neural networks. Second, the processes by which mental representations are generated and selected are very different from the ones that operate in biological evolution. Superficially, ideas and genes are similar, in that both are generated, selected, and transmitted. But the value of an analogy depends on how well it illuminates the domain to be explained, and the comparison with genes only gets in the way of understanding the generation, selection, and transmission of ideas.
Cognitive science has moved beyond vague notions like idea to theories about how concepts, rules, images, and emotions are represented in the mind and brain. (See, for example, my book Mind: Introduction to Cognitive Science). These representations have different structures, arise from different learning processes, and function differently in inference and other cognitive processes. Lumping them all together as memes is just a distraction from explaining how mental representations spread among groups of people.
The biggest reason to reject memes as an analog of genes is that the processes of generation, selection, and transmission are so different. Genetics makes an enormous contribution to evolutionary theory by explaining how variability arises by random mutations, selection occurs by survival of the fittest, and transmission occurs by parents passing their genes to their offspring. But variation, selection, and transmission in minds and cultures are very different from evolutionary processes.
First, cultural generation of ideas is far more goal-oriented than genetic mutation: when new ideas such as the iPad are generated by combinations of existing ideas, it is usually because people are intentionally trying to solve some recognized problem. In contrast, genetic mutation is independent of the environmental problems faced by the organism in which mutation occurs.
Second, selection of ideas is very different from selection of genes, because it is performed by intelligent people capable of using various criteria to decide whether the new ideas are better than old ones. Emotion (hot thought) plays an important role because people get excited about ideas that are new and valuable. Selection of genes is much more indirect, dependent on the survival of the organisms that carry them.
Third, transmission of ideas is far more rapid and widespread than transmission of genes. No matter how valuable a biological mutation is to a species, it takes many generations before the new gene manages to spread through a population. In contrast, a valuable new idea such as the iPad can spread to millions of people in a matter of days through communication mechanisms that are both cognitive and emotional.
Hence, memetics provides only a very superficial understanding of cultural evolution and blocks the way to deeper investigations of the full range of mental representations that contribute to cultural evolution, and the cognitive and social mechanisms by which these representations are generated, selected, and transmitted. Rather than relying on a lazy biological analogy, anyone interested in the spread of ideas should learn more about cognitive social science. Then the concept of meme can become extinct.