Pocklington and Best stated that the characteristics of evolution as mentioned earlier seem to fit memetics intuitively, but that this is not a sufficient basis for a model of cultural evolution. They argue that the detection and description of units of selection is an essential first step towards applying models of natural selection to the realm of culturally transmitted information.
Zarella has done this research for Twitter, he indexes words and content that is likely to to be re-tweeted. He presents a list of the words and phrases most and least likely to be re-tweeted. The lists by Zarella can be considered the units of selection for re-tweets.
Pingback: Tweets die vermelden Slide 24 | Rise of the machemes -- Topsy.com