The Pennsylvania Superior Court just upheld a 2008 innocent verdict against Shiatsu Spa in LeHigh County. State Police received a complaint from a customer of the massage parlor that he had been offered "manual stimulation" (hand job/happy ending) by the girl there. The informant didn't engage in the sex because he didn't have enough money. The State Police provided him with money for four trips to the massage parlor where he had sex with at least two different girls. The Police encouraged him to get more than a hand job, and paid for it. The Court did not rule that the undercover work was illegal, but ruled that the multiple trips were excessive for a successful case and therefore the State Police actions was "outrageous government conduct".
If the Troopers had exercised a little more control, their illegal (but according to them "necessary") actions might have resulted in a conviction.
Law.com - Sex With Informant Voids Prostitution Case