I think it all depends on particular usage scenario. Because potential attacks can involve for example:
- Over/underflow in software handling nfc communication
- The same in regard to application software that is using nfc
- Potential electrical overload of nfc transceiver
- Information disclosure - if there is some "harmless" service code used to test nfc during development
- If nfc usage does not involve human acceptance any vulnerability in application software can be exploited without you even knowing about it
- Without strong authentication device spoofing can be possible
All of these are potential threats to nfc, as to any wireless technology you might say. So as long as you will be aware that this is wireless and it means that anyone has access to it, and you institute a reasonable precautions you should be ok :). As a final word if it is not needed all the time turn it of :).