Memes
Yeah, you see you can do things like gene-centered evolution when you can actually point to a gene and draw a ring around it.
That is pretty handy isn't it? My main problem, though, isn't that they don't "exist" per se -- lots of models don't truly exist in the "real" world, but they do provide useful predictions. I can't see the useful aspect of memetics. It doesn't give much in the way of predictive value, and what predictions it does make seem to end up being either trivial and tautological (ideas spread, no shit!) or totally cranky and false (e.g., Blackmore's contention that the big brain evolved as a "meme machine," a just-so story if there ever was one).
Prediction is the problem. Although I suppose the prediction is that ideas that can be most easily bolted onto someone's existing beliefs will spread more than others. Thought that's almost so obvious it's not worth stating. I just like it in terms of how you can break ideas down into smaller units and see what looks the same in apparently very different activities. Then there's no more need for it to predict anything than music notation needs to predict anything, really. Again, handwavey, but no prediction is better than predictive qualities that are useless.
Though as another point, until we've hacked the brain apart and can understand it I don't think we can call the brain an anything machine. We have ideas about how it works, but the intricate details you need to know to call it a "meme machine" just aren't available yet. You never know, perhaps the neural networks that flash up with ideas will be analogous to genes in that you can point to them and draw a ring around them, then we'll have found the "meme", but that's not terribly likely.
If it has no predictive power, it's not exactly a science in and of itself then, is it? I guess there are somewhat meme-like units in memory psychology called chunks, which are defined by their associational strength with other chunks, e.g. in a random assortment of letters ("ahnwvsnxccd"), each letter would count as a chunk, but familiar abbreviations ("JFK NASA UK CIA KGB") would count as one chunk because of their associations.