This morning I had a preview of iYomu, a social networking site founded by UK ex-pat David Wolf-Rooney. It's currently in beta, and due to launch August 13.

iYomu's line is that it's a social networking site for grown-ups, and it features a clean, simple design that aims to make it easy for its target 25-55 year-old market to sign-up. It's less formal looking than LinkedIn, the grand-daddy, so to speak, of soc-net sites for grown-ups, but less edgy and more newbie-friendly than Facebook.

Yes, it does seem like every second grown-up is already on Facebook, but iYomu has a couple of key points of difference.

One is that there will be no ads (Facebook features scads of madly blinking low-fi banners).

Second is a 'vault', or up to 1GB of free storage for back-up, or sharing photos, videos and music in any common format. If you want a second gigabyte, you'll have to pay $US12.95 ($NZ12.94) a month, which is how the ad-free iYomu plans to make money (though of course the ultimate aim has to be to sell). Wolf-Rooney acknowledges that online storage is not much of a goer on most NZ broadband connections, but his ambitions are global, and the service will be hosted in the US.

Third, the site makes it's grown-ups only stance explicit with a no-kids, R18 policy.

iYomu also has a more involved social profile than most sites, with a set of 10 questions to determine your social 'DNA'.

Other features, such as creating local networks, and networks around areas of interest, will be familiar to Facebook users though - at least with its modest few hundred beta users - iYomu has a cleaner, more graphical way of representing them.

I actually had little idea of how Facebook or LinkedIn worked before I joined them, and only did so because people I knew sent invites. Facebook, particularly, seems to have gone bananas in NZ after ex-pat Kiwis in the UK started using it heavily. And there in lies the rub: no one wants to join (yet another) social networking site unless there are lots of people already on board to invite them, or link to them. How does a site based in little old NZ gain that all-important critical mass?

On this score, Wolf-Rooney and his co-director Frances Valintine are coy.

They say they have a killer marketing idea. One so original and powerful that they've told the US data centre that will host iYomu that it should prepare for up to one million users in the first month, with potential to scale to 10 million in quick time.

As business partners, Wolf-Rooney and Valintine make an attractive couple. Although he's not from an IT background (he worked in the oil and gas industry in Eastern Europe before emigrating to New Zealand around three years ago), Wolf-Rooney has obviously thought carefully about what features his target market would like to see in iYomu, and is does not seem to have any of the usual developer snobbery about beta users' feedback. And through her background as GM of the Media Design School - I learn through her entry on LinkedIn (!) - Valintine obviously knows her way around what works, or not, on a website. Still, from a huddle in a Symonds Street cafe to capturing tens of millions of people's attention in the US, India and elsewhere seems quite a stretch. The IT world is littered with great ideas no-one noticed.

Until iYomu's official launch day, August 13, Wolf-Rooney refuses to give any hint of his killer idea for capturing the world's attention. So until then it's hard to tell if he, Valintine, and their 44 investors are stunningly naive, or do in fact have an unbelievably cunning plan up their sleeves.