In today’s Online section in the Guardian there’s a piece by Jim McClellan on the success of Flickr (a photo sharing and organising website). According to co-founder Caterina Fake, in less than a year its membership has already reached 245,000 and grows at a rate of 5-10% a week.

McClellan discusses the possibilities brought about by Flickr and other social software services on the web, many of which use folksonomies – people-generated tags or metadata – including the impact of del.icio.us and technorati amongst others. These sites help us to organise our own experience of the web as well as brining us together with other people around common themes and interests.

What I’ve been wondering is how sustainable these services are once they break in to the mainstream (if they haven’t already done so). I can’t help thinking each will reach a critical mass where there is too much tagged content to cope with to be useful beyond the personal and “closely” social.

In the same way blogs offer a valuable filter on the labyrinthine plethora of information on the internet (and the “blogosphere” itself), services such as del.icio.us and technorati offer a chance to put a filter on the filters.

What happens next? Is someone already inventing the filters’ filters’ filter?