Should you advertise on Facebook? Or as the P&G marketing chief questioned, should you monetise the place where people dump their partner? Even though P&G may not have had a good experience, several brands have, particularly some of those looking for a direct response. So where does the truth lie?

You do get the sense that a lot of marketing folk believe social networking offers advertising's holy grail. A warm and friendly media where people move effortlessly from arranging that weekend's eating and drinking to debating the merits of the latest mobile PAYG offer, organic yoghurt brands or travel insurance cover. A giant focus group where consumers eagerly discuss ways to save money on gas bills and the best places to shop for interior lighting. And where brands in those sectors can piggy-back the chat.

The trouble is life is not like that. If you are not careful selling on networking sites is a bit like someone coming into a bar and trying to sell you replacement windows. Or life insurance. Er not now, thanks, I'm trying to enjoy my drink and have a debate on the worst ever song lyrics.

People appreciate that Facebook has to make money but advertising that intrudes or is perceived to be 'big brother-ish" will irritate, especially when brands try to muscle in on private conversations. If I am moaning to my mates about how crap my bank is, do I want big corporations monitoring my conversations? Facebook has already had its fingers burnt with Beacon and is now much more wary of the way its data is used.

Contrary to conventional wisdom, you may find 'targeted' advertising even more annoying than generic advertising. Why? Because getting it a little wrong is worse than not trying. It's like Americans calling football soccer. Or Dad believing Coldplay are cool. It's why so much marketing to 'yoof' falls flat. Get the vernacular slightly wrong (is this blog sick, bare or random??) and you're instantly exposed as a fraud. Besides, it's hard for brands to enter 'conversations' with anyone. They have to toe the corporate line and sound contrived when they try to be 'on your side'. Nor can they react quickly enough to chat properly. What they can do, as the BBC, Sagazone, Sainsbury's and countless others demonstrate is facilitate conversations without getting involved.

When it comes to exploiting social networking we need to be sensitive. Brands should be encouraging feedback and comment, delivering more interesting content without pretending to be the consumer's best mate.The big networking sites offer great opportunities but there has to be empathy to tone and sensitivities to privacy or the uniqueness of the medium will burn out very quickly.  However, as with ITV Catch Up, there are cases where consumers accept intrusive advertising as the price to pay for interesting content. But get the balance wrong and consumers will switch and start again with something fresher (wasn't Second Life the last big thing?). No monopoly lasts for long in Web 2.0.