When does one choose stating he/she is DTF versus BDTF? When that individual is up for fucking and beyond, as in, anything or everything will go, and the escapades they are up for may not all include sexual undertones. Perhaps including, but not limited to, adventures of malicious, dangerous, and highly illegal/immoral intent.
Due to unpredictable nature of those titled as BDTF, one should exhibit caution before spending the night alone with what could be one sadistic individual.
This term can be used interchangably with DTF A&E (Down to Fuck: Anything and Everything], yet most prefer BDTF as it is said to "roll off the tounge easier."
Dude 2: No dude, what?
Dude 1: Told Joe she was BDTF. Apparently after the three hours of rough sex, she got a knife and stabbed him. She then proceeded to give him a blow job as she stuck her fingers in his slash wounds and painted on her body with his blood.