Replace "Facetime" with "video conferencing" and your statement would look more plausible, but it is still incorrect.
Facetime in its form, let alone VOIP with Skype and the lot, has been around for a while that environments which are highly exposed to it (in a deliberate and organised way) will already have standards of conduct. Public areas like lounges don't count; I'm referring more to organisations. For example, Skype is advocated in our workplace for some international calls as it is much cheaper than traditional landline. We have a standard procedure when it comes to making phone conversations (i.e. arranging a spare office or what not), but this procedure has existed long before VOIP entered the workplace (i.e. when they just used landline calls), and in fact we all mutually agreed easily on a "procedure" before it was ever formally codified as a procedure in black and white. (In other words, we used common sense and applied ethics).
As far as I can remember, iPhones (or iOS rather) clearly says "Facetime" at the top of the screen and the front camera is automatically activated if a Facetime call is being received, otherwise a different display / heading for a standard call through the Phone app. Also, the ring tones for each kind of call can be different (but I imagine are the same by default, and since there are several who don't change their ring tone from the default, viz. the marimba jingle). I guess that's kind of moot when your phone is in vibrate only mode.
