The PO of my new (to me) boat kept it on a mooring can. I can't vouch for how careful he was or wasn't, but both sides forward have tons of dings and scratches around the water line from (I assume) banging into the can. The broker even had a name for it: called it "can rash".
Just my very limited experience. YMMV.
My familiarity with public mooring setups is limited to mooring "balls" which are not metallic. I never knew that there were "cans" in use elsewhere. Seems to be a bad choice by the mooring field owners.