Monitor bandwidth usage on user by user basis

[zeroion <zeroion@gmail.com>]

Hello all,

Is there any way to monitor and log each user's bandwidth usage (data
transferred)? I know that I can use scripts to monitor how much
bandwidth each user consumes through HTTP, MTA, and FTP logs, but I
would also like to monitor how much bandwidth a user consumes through
the command line (i.e., wget, lynx, nc).

Thanks,
Stephen