Not that you could get a coffee-table book out of it, but every few weeks or oftener I encounter a used-up vacuum cleaner put out to pasture somewhere in town. Today’s example: a canister model apparently abandoned on the sidewalk along Monterey Avenue. What’s going on with these things? Maybe they’re too awkward to throw out — the trash haulers probably won’t take them in the regular weekly pick up. Maybe there’s some sort of emotional attachment that might equate discarding a well-loved vacuum cleaner with taking a pet to be put down. Maybe the vacuum owners have talked themselves into believing that their old machines still have a few months of useful life left in the service of some thrifty passer-by. Maybe all of the above.