Another reason to hate Adobe

Does anyone know what I did that installed this Adobe DLM into Firefox 3.5.3 on Windows XP? I’m about to disable it, but I’d really like to know how the loathsome weasels at Adobe managed to cram it into my Firefox Add-ons without me noticing. Is it something automatic when I updated Adobe Reader? Did I not unclick a box that I should have unclicked?