Not a bad thing necessarily, but some part of the plot, and usually with things going awry or emphasizing the scammy nature of blockchain.
Examples: Shameless season 11, The Simpsons S31E13, Superstore season 5, the good wife S3E13, greys anatomy S14E8, big bang theory S11E9, Billions season 5, some later seasons of Mr Robot, etc
In numerous shows these days AI is the big bad thing. Before that it was crypto. In the 1980s every bad guy was Russian, etc.