The real question I think should be: can prostitution benefit from bluetooth and bitcoin?
If in Saudi Arabia, bluetooth can be used to flirt and circumvent bans on men and women associating together (
http://archive.newsmax.com/archives/ic/2005/8/12/94234.shtml )... then maybe someone can find a way to use bluetooth as a surreptitious way to make a bitcoin payment to someone unobservably.
Maybe someone makes a decoy Contacts app where the guy asks for the girl's "number" and puts into his "contacts" app... a relatively innocuous exchange that would be entirely ordinary in public... then after the girl's phone vibrates briefly for no reason, the two suddenly go have sex.
What happened was the decoy contacts app invisibly finds and talks via bluetooth to an app on the girl's phone, gets a bitcoin address, makes a payment to it, and an invisible app on the girl's phone buzzes to indicate the payment was received. The phone number he got was probably not a real telephone number, but was just a step to make sure the guy paid the girl he's talking to and not some random stranger's phone within bluetooth range. (And, a few digits of the number might stand for the amount to pay.)