I have both factions 1.6.6 and precioustones 9.03 with craftbukkit 1.2.5 R1, and my users can /f home right out from under a prevent-teleport field. I know its possible to block this command, because essentials jail does it pretty well. Thanks for making such a great plugin!
Edit: updated to factions 1.6.7 and PS 9.10 with no improvement

Added "command-blacklist" flag to the dev version of the plugin. You can use this to block the factions home.