I don't think so much it is lack of numbers, as Ibiza is just as popular with clubbers as it has ever been.
I think Barbie has hit the nail on the head, there simply aren't enough people to go round all the nights. Of course the most popular few nights will always be busy, but its the not so big nights which were very good that are suffering and, us the clubbers because of it.
I think the blame is partly with the clubs and partly with the promoters, the promoters have pushed things one step too far, there are too many nights now, and what could be really good nights are suffering. The clubs should be more selective about what nights they have as well, although they can't be blamed for taking the money. Its not so much the prices, its just the amount of nights at them prices that is the problem.
Take Pacha for example, it seems since Danny Whittle took over as music director things have gone bonkers, you can now go to Pacha to a US or UK night from Mon-Sat, OK Pure Pacha is for the 30th Anniversary but is still UK/US DJ based, that is just ridiculous, they are going to ruin the club for themselves by being greedy. What happened to the days when you could got to Renaissance on a Wed and MOS on a Friday and that was it as far as UK nights went at the club, at one point there was only MOS on a Friday.
Hopefully there won't be as many nights next year and it will be back to normal. Also I think El Divino is closing.
When I first went to Ibiza, there were basically 5 major clubs to go to, 6 if you include Es Paradis which had a couple of good nights back then. They were of course Pacha, Space, Privilege, Amnesia and El Divino (which had only just opened itself about a year or two before). You went to Manumission on a Monday, Moneypennies on a Tue, Renaissance or Clockwork Orange on a Wed, Cream on a Thur, Ministry on a Friday, Sat didn't have any big nights (although there were Spanish ones) and the Sunday Session at Space.
You've now got the addition of Bora Bora, I know its a br but it pulls in the crowds, DC10, Eden is popular with the trance/hard house heads and Pin Up and Underground plus loads more cool bars/places where lots of people spend the whole night and don't even go clubbing sometimes. On top of all that, you can go to one of the big clubs most nights of the week and they have decent nights on.
Something has got to give, hopefully the new clubs like Pin Up will lead the way, with cheaper entry prices and drinks and a more friendly atmosphere, I feel this is the way forward. Hopefully the number of nights will come down and the prices will come down.
Time will tell, one thing for sure in my mind though is that Ibiza will be alive and kicking for a long time with the clubs and vibe that are there, its just going through a bit of a transition, a bit like what has happened in this country.
Hopefully for the better as that is the way I see it has gone in the UK.
Sorry for the long post!!