Very few things divide opinion as much as social media.

To the evangelists, it’s the ‘great white hope’, the future of interactive marketing. To others, it’s the ultimate in snake oil sales. To online retailers, social media represents a fantastic opportunity to spam a willing target audience of millions. However, tread this path at your peril!

The reality of social media is not quite as straightforward. Truth be told, most online retailers are involved in social media for all the wrong reasons and as a result are seeing little or no reward from it.

So here are my top five reasons why online retailers should not use social media.

1. Because it’s free

There’s no such thing as a free lunch, so the saying goes, and this truism is certainly the case with social media. Just because a Facebook page or Twitter feed costs nothing to set up and run at the point of use does not mean it won’t require investment.

Strategy, understanding, positioning and brand awareness, are all critical parts of a good social media output, with execution only being relevant in their context.

Our overseas office recently ran a campaign for Lexus engaging bloggers on the hybrid car debate. This involved setting up their own discussion hub then integrating with a number of existing social media platforms and hiring expert bloggers (Bob Geldof being one of them) to start the debate. This was not a free exercise, but because it was strategically and properly thought through and executed, it exceeded every one of Lexus’s targets and KPIs.

2. Because everyone else is doing it

Nothing in life is more powerful and more dangerous than peer pressure. The clamour for brands to be involved in social media is deafening, with marketing managers across the globe all stating that they need to do ‘something on Facebook’ with no clear picture of what that something is, but more critically, what it is intended to achieve.

Just as you wouldn’t commission a web agency to just build you ‘some sort of website’ but rather work closely to a defined brief, also you need to have a clear idea of what you want social media to achieve before you head off and start doing it.

Until you have that, then it’s probably better to do nothing at all.

3. Because it’s a new way to advertise my products

Social media is not a broadcast channel. Let me repeat that: social media is not a broadcast channel.

No one is going to want to subscribe to a Twitter feed, for example, that simply spits out broadcast messages telling everyone how great your products are.

Social media is about engagement, listening to consumers, responding positively to their views and comments, good and bad. It’s about adding value to consumers lives, whether through content, freebies or customer service – not simply pushing your wares.

What’s amazing is that this really hasn’t seemed to sink in to brands yet. I guess old habits die hard. Just type any brand you know into Facebook and find their fan page. See how bland they are and lacking in engagement. Find one that does it well and the difference is startling.

4. Because it has a global reach

Does your business have a global marketing strategy? How are you perceived in other countries? What does your brand mean to internationals, if anything? How can you meet and satisfy global consumer demands?

If the answer to any of these is anything but crystal clear, then don’t kid yourself that creating a Twitter feed is going to open your brand up to the world. Also, remember that social media is becoming increasingly localised, with the trend moving towards more geo-locational search and interactivity. New services, like Foursquare, are using social media to encourage real-world interaction with the user’s local areas and are set to be a powerful trend in how we relate to social media over the coming year.

5. Because it will increase sales

I have to be careful here, as social media, like any effective PR or marketing strategy should, at its heart, be about increasing sales.

However, much like marketing and PR, this can be quite subtle and indirect. For example, a couple of years ago we built a local store extranet (sort of Facebook but for their network of offline stores) for one of our clients. This had limited direct commercial functionality other than to help the stores promote their events and give staff a platform to speak about the products they were passionate about.

Did it increase sales? Pretty hard to say directly, but it was hugely popular with both staff and customers and we can only assume the good will it generated was a positive asset for the businesses growth.

This is how social media can help, not by how many people click on a link on Twitter to buy a product but how it can help you position your business as an open, intelligent, trusted and knowledgeable beacon of hope in a sea of cynical commerce.