On the positive side it can cover the sex for $'s issue as LE/politicians are not on top of or have much of a clue as to what bitcoins are our how to legislate or enforce it. So in theory if you've paid with a bitcoin currency then it really is just a casual encounter.  

On the negative, bitcoins are really a vapor currency as their is no real solvent assets that back its true value. Value is determined by supply and demand and can fluctuate greatly (I may add is very volatile atm). If the gov't seizes a large bitcoin holder involved in some illegal activity such as drug trafficking it can impact market value greatly. It's also greatly influenced by perception.  

My advice to clients/companions is do your research on the bitcoin market place. Understand it's trends in fluctuation. If you choose to open a bitcoin wallet get with a reputable exchange. I'd also wait until more bitcoins are in circulation as it will soften the volatility a little. Currently there are 11.5 million circulation out of a total of 21 million.

The big problem is that the value of Bitcoin is highly volatile.  How would you like to get $300 worth of bitcoin at the beginning of a session and learn it's worth $3 at the end?  (Of course, it can also go the other way).

Most prostitution laws, I believe, are phrased in terms of the exchange of sex for something of value.  If they weren't written that way, we'd all be bringing bags of groceries, gift cards, etc.

Prepaid escorts via PayPal or similar service could work well. The time relation to act is far removed, so hard to prove qui pro quo. Providers would not be allowed to Upsell since the session was prepaid. No funds brought to or exchanged on site. A parallel market of information (TER) keeps everyone honest and informed. The client would truly be paying for your time and nothing else.  

How does the LE sting this?