The concept of memes was interesting when I first heard it, became metaphorical the more I learnt about it, and now I consider it as not having any explanatory power. Yet there is still some superficial plausibility to it the idea, and that was highlighted on a recent episode of The Big Bang Theory.
In the episode, two of the characters decided to spread two rumours to see whether or not there was a differential success in the rumour spreading among social groups. One, a hot piece of gossip, the other not. Of course the gossip spreads and memetics is shown to be a success!
If that's all memes are, then it's not really saying much. Meme would be a vague metaphor, useful as a short hand for ideas that spread quickly but little more. It's hardly showing the value of memetics, and especially not of the analogy between memes and genes and the invocation of a Darwinian framework. In other words, if memes are like genes then we should see memes modifying themselves in order to continue to thrive and becoming better replicators.
It's a lot harder to think of examples of the latter case. It's likely that there are examples out there (the term meme itself is probably a good candidate in that it started out as a Darwinian replicator and has changed to become a term for a rapidly-spreading cultural unit) but in terms of what people mean when they say meme, it's not really anything more than a vague metaphor.
It seems that meme has become somewhat of what Dan Dennett calls a deepity. That is an idea or phrase that is true in a trivial sense, and in another sense sounds profound but is intellectually hollow. Of course some ideas spread better than others, but the earth-shattering implications of memes just doesn't pan out.