Memetics, or the study of memes, is useful for its power to draw disparate research fields into the study of the mind. Parasite ecology helps predict the auto-toxicity of a meme using a distinction between horizontal transmission and vertical transmission. Parasites that pass from parent to child (vertically, that is) evolve to promote themselves by promoting their hosts, for example beneficial bacteria. Parasites that pass between members of the same generation (horizontally) need to move fast, have no incentive to help their hosts, and tend to be quite autotoxic.
A practical upshot: if you are in the market for a religion, stay away from the ones that are looking for new members. Go find a religion that is quite happy to mind its own business.
For example, many less westernized forms of hinduism, hold that it is simply impossible to "become" hindu through an act of conversion; you have to be born into it. Other forms of hindism in the west have all kinds of swamis and gurus hot to infect new followers. Guess which flavor parasite ecology indicates would be more personally rewarding?