Sometimes, things are bad. This is known. Said things are not good.
History
It is widely thought that bad originated from BAD™ reactors, which are suspected to have been yielded from retroactive BAD™ reactor influence, due to them being bad.
Examples
Some examples of bad things are gollark and GTech, as well as BAD™ reactors. The continued deployment of IPv4, as well as gollark's opinions, are also widely held to be examples of bad.