Call centre staff, telemarketers or other such people who suck the life force out of you by either:
a) Keeping you on hold for a significant portion of your life
b) Incessantly chatter away until you either fall asleep or die from boredom.
John: "Can you believe I was on hold for over 2 hours trying to get my phone connected ?"
Jane: "Yeah, those call centre vampires sucked the life out of me last week trying to sell me long distance. I can't remember anything between Monday and Wednesday "