Thanks! Erasing the fsevents database made Time Machine speedy again!
Problem: On my Mac OS X 10.6.8 system, TimeMachine (TM) minimal runs — this is when almost no files change between consecutive runs — always took about 15 minutes as opposed to ~1 minute, which it had taken, when TM worked properly.
Investigation: Monitoring with the excellent and free GUI
fseventer had shown me, that backupd always created a bunch of hardlinks for folders and files, which hadn't changed for months, at each time TimeMachine ran in the last months!
Even though the fsevents database and its contained files had a timestamp of the current day, the database seems to have been corrupted, carried along some very outdated info, months or even years ago, which caused the unnecessary copy/hardlink operations.
Solution: After having wiped /Volumes/*/.fseventsd/ TimeMachine ran once with a deep traversal as UUIDs did not match, but henceforth, all quick runs again only take ~1min, as opposed to those annoying ~15min!