Only the most blinkered (or immature) of Spice Girls fans couldn't have seen that the group was destined to splinter at some time or another. Geri Halliwell's surprise departure from the most financially successful and commercially exploited girl group of the decade was the first crack in what is bound to be an ever-widening fissure. Seasoned pop music observers could see it coming a mile off.

In the June issue of Q magazine - hardly a publication that the group's predominantly under-14 female fan-base reads - Geri was asked if the Spice Girls could carry on if one of them left the fold. She replied: "We'd have to think long and hard about it if anyone did leave, but, no, I don't think we could carry on. It wouldn't be the same."

In the same article, Emma Bunton and Victoria Adams claimed that the group was all about friendship and family, and that they would "talk everything through" if such a situation arose.

As we now know it did, but the women weren't necessarily up for a post-divorce heart-to-heart chat. Instead, lawyers did the talking.

Pop music, like any other consumer item you care to mention, has built-in obsolescence. Depending on the durability of the music (which in turn relies on the quality of the constituent parts), it lasts either for generations or breaks down after a limited period, spawning, respectively, the frequent classic hit and the one-hit wonder. Another crucial factor in the lifespan of a pop act is perhaps that most unpredictable of beasts: the fans.

Fans come in two distinct and separate packages: loyal and fickle. Generally segmented by age, the loyal fan remains true to their musical tastes. Their likes and dislikes are formed by a knowledge of what they perceive to be good or bad. They are essentially of the "I don't know much about wine, but I know what I like" variety.

The fickle music fan has, generally speaking, yet to formulate any real points of cross-reference or comparison. They tend to dive headlong into their pop music experience with little or no perspective, enjoy it for it is (or isn't), quickly tire of it, and then dive into the next bright, big thing with no guilt, shame or embarrassment whatsoever.

Pop music, however, thrives on its own ephemerality. While there is clearly nothing transient about the music of The Beatles or The Who, or of existing pop/rock acts from the 60s such as The Bee Gees, The Rolling Stones, Elton John, and Pink Floyd (who, bucking pop history, has prospered despite the departure of its main focal point, Roger Waters, in the 80s), the line between what lasts and what doesn't is a thin and nebulous one.

Historically, bands that have effectively grown up together - whether through school, college, or communally-bonding garage rehearsals - are the ones that have the creative glue and genuine friendship that holds them commercially and personally together through the years.

There's also something tangible and authentic about songs that have been written by either a single person or a team of like-minded people, however insincere or manipulative the reasoning behind them.

Manufactured pop groups like the Monkees and the Spice Girls (and Boyzone for that matter), on the other hand, are little more than bright marketing ideas that inevitably fizzle out after the novelty wears off. There is nothing organic about them that is to be found in your typical school-friends' band. Hard work and talent might be there, but so are personality clashes.

The Songs, too, suffer from being written by a hired committee. There's no guiding hand that nurtures a song from start to finish, and there's rarely any lyrical cohesion (or insight) in the songs that make them genuinely interesting or memorable.

Geri Halliwell's departure from The Spice Girls wiped about £100 million from the share value of EMI during the week, the company's shares falling by 10p to 508p. Alex de Groote, of stockbrokers Albert E. Sharp, has the view that every record label is only as good as the acts it has on its roster.

"The clearest comparison is Take That," he authoritatively commented from the littered floor of the Stock Exchange. "Once a key member leaves, it shortens the lifespan of the group."

The Labour MP for Harrow West, Gareth Thomas, asked ministers to urge Geri to reconsider her shock decision (he was serious, apparently), while a Samaritans spokesperson serenely suggested that fans of the group "share their grief".

Presumably, all these people have their fingers on the pulse of a cultural corpse, for the reality of the situation is that fans of the Spice Girls (who, when pop history is being updated in a few years time, will be credited only to having made slut clothes fashionable) have long since forgotten about their grief.

The latest new girl band to catch the fans' short attention span is B*witched a teenage "Irish hip-hop pop" quartet from Finglas, north Dublin, who shot straight to No 1 in the UK charts this week with their debut single. Its title? C'est La Vie.

A perfect title for such an unfair, unreliable world as pop music, don't you think? What a pity the Spice Girls didn't think of it first.