bottom feeder: n.

1. An Internet user that leeches off ISPs - the sort you can never provide
good enough services for, always complains about the price, no matter how
low it may be, and will bolt off to another service the moment there is even
the slimmest price difference. While most bottom feeders infest free or
almost free services such as AOL, MSN, and Hotmail, too many flock to
whomever happens to be the cheapest regional ISP at the time. Bottom feeders
are often the classic problem user, known for unleashing spam, flamage, and
other breaches of netiquette.

2. A person who has more or less failed in life and is at peace with
it.
"He's a no-good bottom feeder!"