The police in some areas - when I was paid to know and give advice about this sort of thing, one of my first questions was always 'where are you?' - have been known to threaten places with PoCA, but it is basically an empty threat. Now that several 'we're on a mission from ghod / some moral crusade' men like Tim Brain have resigned from being Chief Constables for one reason or another, it's much rarer too.(Original post by DanB1991)
Websites can fall foul of the Proceeds of Crime Act 2002 and also Sexual Offences Act 2003, thus the specific wording used in adverts. The person advertising the acts wouldn't be causing the offence, more the person hosting the advertisement.
Where's the offence in the SOA? Websites cannot control anyone's sex work, therefore they can gain from it.
I'm guessing you haven't seen some of the gay press with its 'here's a picture of my erection, here's what it'll cost you' ads.
And actually passed?