Technology

Especially toilets. They know what they did...

This is probably more of a failing of infrastructure and planning than technology. But I think if we only handle advances in technology as a thing on paper and not a thing in society used by people, then we miss an important, but simple point. Technologies are used by people and they is the only way they can change society.

Any case, toilets ruined London for a couple of decades:

As the population of Britain increased during the 19th century, the number of toilets did not match this expansion. In overcrowded cities, such as London and Manchester, up to 100 people might share a single toilet. Sewage, therefore, spilled into the streets and the rivers.

This found its way back into the drinking water supply (which was brown when it came out of the pipes) and was further polluted by chemicals, horse manure and dead animals; as a result, tens of thousands died of water-borne disease, especially during the cholera outbreaks of the 1830s and 1850s.

In 1848, the government decreed that every new house should have a water-closet (WC) or ash-pit privy. "Night soil men" were engaged to empty the ash pits. However, after a particularly hot summer in 1858, when rotting sewage resulted in "the great stink (pictured right in a cartoon of the day)", the government commissioned the building of a system of sewers in London; construction was completed in 1865. At last, deaths from cholera, typhoid and other waterborne diseases dropped spectacularly.

The Great Stink only arises because of the development of a sewer system that piped all the sewage to the Thames. And it didn't stop with the stink:

Despite Bazalgette’s ingenuity, the system still dumped tons of raw sewage into the Thames - sometimes with unfortunate results. The death toll from the sinking of the pleasure boat Princess Alice in 1878 would certainly have been smaller if it had sunk elsewhere on the Thames. As it was, it went down close to one of the main sewage outfalls. Approximately 640 passengers died, many poisoned rather than drowned. Horror at the deaths was instrumental in the building of a series of riverside sewage treatment plants. [Science Museum]

So that's just one example of toilet technology causing a mess. I bet there are others such as the need for an 'S' pipe. But ultimately, technological improvements require a little foresight, insight, feedback and a lot of social power.

Name 5 that did not have sweeping adverse consequences, with accompanying sources. I will even accept Wikipedia pages if they have attributions. Make sure they are major ones that really shaped the course of human existence moving forward from their introduction.