Sony BMG copy protection rootkit scandal from 2005 (en.wikipedia.org)

I don't claim this is something to be proud of, but from that scandal to this day, I buy nothing from Sony, and neither does my company. Trust counts.

I actually consider the Sony BMG rootkit as the beginning of commercial malware. The antivirus companies knew it existed, but did not flag it partially because it was by a legitimate company with a legal department, and not an unknown developer or dubious organization like viruses up to that point.