Memes
I use the word "meme" to describe an idea that has spread almost biologically, infesting millions of minds in a short time, apparently without going to the trouble of passing through any form of gauntlet of reason in the brain. Many of these are even self-contradicting. Given the internet and the mass media, there have been a lot of these in recent years. If you have a better term, I can use it if it bugs you that much.
This is probably not a precise usage if you are actually into "memetics."