If your Launchpad was a mangled mess with 8 pages of everything that could possibly be ran as a program on your Mac like mine when you upgraded to OS X Lion, you’re annoyed you didn’t find this before you spent a ridiculous amount of time organizing it to accomodate your OCD tendencies. Wait, maybe that was just me. Either way, it would have been nice to know this before, still glad I know it now though.
Run this command in Terminal.app to wipe Launchpad clean
sqlite3 ~/Library/Application\ Support/Dock/*.db "DELETE from apps; DELETE from groups WHERE title<>''; DELETE from items WHERE rowid>2;"; Killall Dock
Run this command in Terminal.app to rebuild the default database
rm ~/Library/Application\ Support/Dock/*.db; killall Dock