Comment by cosmic_cheese

This makes a lot of sense if public participation is actually desired. Links need to be short, snappy, and memorable so they're easy to either type into a smartphone on the spot or be recalled at some point later when one has a spare moment. This kind of link is also more likely to spread via word of mouth.

Traditional link shorteners only meet one of those requirements. Random strings aren't going to be remembered and the chances that they'll be mistyped is substantially higher.