I don't know why there are two rules for Logitech bluetooth devices, but the first rule for them in/lib/udev/rules.d/70-hid2hci.rules misses at least IDs 046d:c70b and 046d:c70c. Kernel 2.6.40.4-5.fc15.x86_64 shows up a hiddev-device for such an adapter if the dongle is in HID-mode (after booted). So if it should be possible to put such an device into HCI-(bluetooth-)mode (which I assume is reason for that rule), the rule has to be expanded to use ATTRS{idProduct}=="c70[35bce]" instead of ATTRS{idProduct}=="c70[35e]" The problem is related to bug #635244. Because the rule is currently not working for (some) Logitech devices, they are only used in HID mode (no bluetooth), so users of those devices aren't affected by bug #635244, but it means too they can't use the bluetooth functionality.
This is already fixed in the bluez-4.96-3.fc16 update which will be pushed to F-16 as soon as the beta freeze is lifted. *** This bug has been marked as a duplicate of bug 653244 ***