|Daniel Kaluuya in "Fifteen Million Merits" (Black Mirror Season 1, Episode 2)|
The episodes often have themes that deal with sex, but the themes are rarely presented in a sexual way (i.e. included because "sex sells), rather they are typically an important part of the story and deal with themes of sexual exploitation or the negative role of technology to unnaturally deliver sexual stimulus to a negative end.
Without spoiling the episode, Fifteen Million Merits, by far one of the most futuristic feeling episodes presents an alternative dystopian world where part of mind numbing tools used on people is pornography and as part of it's story telling a central character is manipulated in a way that leads to further exploitation of a sexual nature.
Many of the time, these topics appear as part of the hidden side of the internet, which is a key part of "Shut Up and Dance" (Season 3) which involves internet usage for less than wholesome things leading people to be placed an exploitable position. Where an episode like this shows people using technology on their free will, other episode such as "Men Against Fire" (Season 3) have military members being exploited by creating false sexual realities as part of the way there minds are used to exploit them and present false realities.
When I think about the comparison of Black Mirror to the The Twilight Zone this is one of the key differences -- in some ways, I chalk it up to edginess that is created in Black Mirror that reflects the producers desire to be shocking, but on the other hand this is also part of the modern technological dilemmas presented. It seems that every new technology ends up having a risk for sexual use, which we talk about at time, particularly when we talk about risk for raising children and providing them technology. But on the other hand, it's not just children -- it's a societal risk that has been introduced that is changing not only our social sensitivities ("The National Anthem," Season 1) and creates not only immoral opportunities but new criminal opportunities ("White Christmas," 2014 special).
There's certainly items all throughout the Black Mirror episodes that warrant discussion, often because of the way they make us feel uncomfortable in the vieiwing, and the topics that flow from Sexual Themes are no exception.