Dropped as in not in the serps?
Dropped as in no pagerank or lowered pagerank or lower keyword positions?
Dropped?
Joeyl a great number of sites were dropped from the SERPS by Google during its last two major algorythem changes (Florida and Austin)
The sites themselves still have high PRs and back links they just no longer occupy positions in the serps where anyone would see them. So there is little reason NOT to experiment on them…