Is that they serve themselves, much like the 'selfishness' of genes. Some memes replicate because they're good for their group, e.g. leatherworking, tool use. Others replicate just because they're good replicators. I think it's obvious enough how the 'blow yourself up to kill infidels' meme doesn't do its 'host' any favours.
Humanity rebelled against genes, will be interesting to see if we can do the same to memes. Given that our consciousness itself may be inextricably linked to them it might be logically impossible to do so