The details change and it may be apocryphal, but it's worth recounting the story of Picasso's napkin. The artist was, apparently, sitting in a Paris café when a customer recognised him and pleaded with him to execute a doodle on the back of a serviette. Picasso obliged and, handing the work over, asked for $10,000. "How can you possibly ask for that much money, the picture took you less than a minute?" "On the contrary," replied the artist. "It took me 40 years."

Regardless of which side of the "genius/my-kid-could-do-better-than-that" debate surrounding conceptual art you stand on, these days, few would argue with paying tens of thousands of pounds for a Picasso. But there are other artists (let's not name names), who seem to have taken the whole "one minute/40 years" thing to heart.

Are we to believe that childlike splashes and squiggles, rows of bricks, saucily arranged fruit, lightbulbs, toy soldiers, rotting carcasses or craftily juxtaposed everyday objects all pass the Picasso test? And if artistic genius really does exist, is it possible that it could manifest in hundreds of people within a very short space of time? Of course not.

A couple of weeks ago, the German painter Gerhard Richter told the world that the prices currently being paid for works of art were "just as absurd as the banking crisis. It's impossible to understand and it's daft."

So for anyone currently seeking an "investment piece" at the Frieze Art Fair in London, the problem is in knowing which urinal will turn into a defining emblem of Duchamp-like deception, and which is just a place to empty the bladder. There is no easy answer, and in that grey area many a fool and his money have been easily parted.

In their manifesto, the Stuckists ("Against conceptualism, hedonism and the cult of the ego-artist") claim that: "Art that has to be in a gallery to be art isn't art." And they might have a point. But none of this answers the million-dollar question at the heart of this debate. Where do you suppose Picasso's napkin is now?