Another warning, albeit with a fix… the procedure described above only works if your database is entirely MyISAM tables, I think. InnoDB tables are not actually stored in the directory named after your database. I followed this procedure to revert a rather stupid change I made that deleted imported data, and lo and behold after restarting with the old database… I still had the new database.
The solution is simply to skip steps 5-7, and just restart the server after you've restored the "data" folder from Time Machine. After you verify that it's working, then you can delete the data-bak/ folder that you've made.