As someone who has no desire to get involved in social networking internet sites, I am somewhat baffled by their allure. Nevertheless, I am prepared to accept they are fun, sometimes useful and mostly harmless.

I do, however, wonder what impact they are having on marriages. Just as Friends Reunited publicly resulted in couples breaking up after one partner tracked down their first love on the site, so the likes of Facebook make it acceptable for people to add as “friends” ex-lovers and erstwhile work colleagues. The provisions to update your “status”, so people know what you’re doing and thinking, and indulge in real-time “pop up” chats can quickly and easily lead not only to a renewal of friendships but also lapsed or previously thwarted romances.

There’s another, less obvious danger, too: I’ve heard stories of couples spending their evenings communicating via the internet – even though they’re sitting only a few feet apart. Yes, really!

Call me a killjoy, but I don’t feel this can be particularly healthy for a relationship. It’s one thing to use a laptop to keep in touch with friends and family around the world, but it’s quite another to talk to your spouse on Facebook instead of face-to-face.

Those who do this insist it’s just a bit of fun, but I wonder about the long-term effects on their relationships. Many people spend a good part of their day at work staring at a computer screen and communicating with business associates via email. That’s why it’s more important than ever to ensure you don’t lose the capacity to talk meaningfully to people in person – be they colleagues or near and dear ones.

What’s more, leisure time is traditionally associated with doing something different from office tasks – such as cooking a meal, reading a book, playing squash or watching TV. Having conversations with your spouse, whether about your day or your shared dreams, is an essential ingredient for a good marriage. Just as fast food is no substitute for a home-cooked meal, so swapping banter on Facebook is no substitute for chatting to your partner while curled up together on the sofa.

Intimacy – verbal, emotional and physical – is what makes marriages work, and however innocuous it might seem to spend hours tapping away on a keyboard, it is no way to develop and deepen the relationship that means most to you.