A classic example of this involves promoting interactions between hosts. In the organic realm, rabies makes hosts want to bite each other while toxoplasmosis makes hosts unafraid of each other and attracted to each other's urine. In the cultural realm, missionaries seek out potential converts and teachers seek out pupils. In each case interactions between hosts are promoted by symbionts - because they need such interactions to reproduce.
Another example is reduced fertility. Many parasites compromise host fertility - probably since host reproduction uses resources which might otherwise go into symbiont reproduction. Many parasites go in for complete host castration - they are called "parasitic castrators". Many cultural symbionts also reduce host fertility - as seen in the demographic transition. Places like Japan where there are many memes have sub-replacement fertility.
This post is mainly proposing terminology. I think we should call these shared interests a "consensus". It's the consensus of the symbionts that the hosts should get out more, meet more strangers and not have kids of their own. Of course, "consensus" is not meant literally here: no-one is suggesting that the symbionts communicate via town meetings. The consensus might be different depending on which group of symbionts are under consideration. Gut bacteria might have a consensus that the host should go the the smallest room more frequently and spend more time there - while cultural symbionts might have a quite different consensus. We could call the cultural symbiont consensus the "memetic consensus" for short.