Massimo Pigliucci puts it very clearly (boldface mine):
Wilson’s next move is to invoke Richard Dawkins’s idea of ‘memes’, or units of cultural evolution. If culture is made of discrete units that can replicate in the environment of human society, perhaps there is a way to bring evolutionary theory to bear directly on culture. Instead of genes (or epigenes), we apply Darwinian principles to memes. Unfortunately for consilience, the research programme of memetics is in big trouble. Scientists and philosophers have cast doubt on the usefulness, even the coherence, of the very concept. As my evolutionary biology colleague Jerry Coyne has said, it is ‘completely tautological, unable to explain why a meme spreads except by asserting, post facto, that it had qualities enabling it to spread’. We don’t know how to define memes in a way that is operationally useful to the practicing scientist, we don’t know why some memes are successful and others not, and we have no clue as to the physical substrate, if any, of which memes are made. Tellingly, the Journal of Memetics closed a few years ago for lack of submissions.
Hopefully, he won’t take an ax to LOLcats though.
And I had some thoughts on the fallacy of the meme concept a few years ago.