Sorry. They don't actually have anything to do with funny American football or even men with sticks pushing boats along in Cambridge.
I shall henceforth endeavour to clear up this matter.
According to the Oxfort English Dictionary of All Things (TM)
Punter/’pΛntə(r)/n, 1 a person who gambles or lays a bet. 2a colloq. a customer or client. b colloq. a participant in any activity; a person. c sl. a prostitute's client. 3 a point in faro.
That, ladies and gentlemen, was a html nightmare. (No idea what this "point in faro" is, but I digress."
So there we are. A Prostitute's Client.
This will also give you an explanation for the naming of the splendid "Punternet." Which is basically a "Who's Who in the world of hooring" or, if you like, "Which Hoor." (I reckon such a mag would sell very well on the top shelves of the Grey Toon).
(I wasn't going to put any links to it, in case my family read this, but I've gone over a year without them looking it up so far and I've got my Bloggy Nookie section in the sidebar, so why the hell not!)