The list has stood up well over time, despite being misunderstood by confused critics. However, these aren't the only attributes which many successfully-copied entities tend to possess.
If adding to the list, "sociability" and "brevity" would be at the top of my list.
Most successfully-copied entities are sociable - meaning that they tend to associate with other genes or memes. Some use direct hitchhiking to spread - through being components of successful gene or meme complexes. Others use phenotypichitchhiking. Unsociable loners exist, but they are not the main players.
Lastly, brevity counts. Consider the following searches:
- "to be or not to be" - 2,810,000 results;
- "to be, or not to be? that is the question" - 250,000 results;
The shorter string is more common - simply because shorter strings tend to be more common as a statistical rule. This is true for most genes and memes - and can be expected to be true of other copied entities - provided they are sometimes divided.