Upload ratio
The BBS rule that you could download only so many files or kilobytes per upload — an early attempt to keep freeloaders in check.
A board with a big file base attracted callers who dialled in, drained it and never came back. The sysop's answer was a ratio: three downloads per upload, say, or kilobyte for kilobyte. The software kept count automatically, and anyone who dropped below the line had to wait or upload something first. Prized files might earn bonus credit; dupes and junk could be clawed back.
The system bred its own problems. People uploaded renamed old files, split archives and outright garbage to pad their numbers, and sysops spent hours cleaning up. Elite access often meant the ratio was waived altogether. The same logic lives on in private torrent trackers, where the ratio is measured in uploaded traffic instead — and the leecher is still the villain.