I perhaps shouldn’t have been surprised as I was at the volume of press coverage triggered by figures from Nielsen yesterday, claiming the first ever monthly fall in Facebook users in the UK. According to the research firm only 8.5 million unique users in Britain spent time on Facebook in January 2008, compared to 8.9 million in December - a 5% fall.

Speaking to Forbes yesterday I was keen to stress that we shouldn’t jump to conclusions based on a single set of figures, but at the same time we shouldn’t expect the growth of social networks to continue at such a phenomenal rate. Despite this hiccup Facebook fans have been keen to point out that the audience is a remarkable 712% higher than in January 2007 and 9% larger than at the end of October 2007. This contrasts with an apparent 9% fall for MySpace over the course of last year.

What these figures have done is moved the focus onto the next stage of social networking development. A number of commentators have suggested that the future of social networking sites lies in them becoming more niche. The million dollar question is which niche?

The sub-25s may be more relaxed about privacy and advertising but arguably more promiscuous over which ‘cool’ site to spend their time on. Older professionals may be more stable and attractive to brands but generationally far more sensitive to how advertisers take advantage of their personal data.

In any case there’s no need to perform the last rites over social networking quite yet.

UPDATE: Henry over at Tamar has some interesting analysis predicting that next month should see the Facebook numbers recover…