Stumbled on this thread whilst googling "Class Action MobileMe"... I half expected some 'ambulance-chasing' US lawyers to be putting something together.
I've been a .Mac user and and less than happy that since "upgrade" to MobileMe, I can't access my webmail on my work PC since it uses IE6. Also, when I travel, I need the flexiblity to be able to log onto any PC and check my emails and MobileMe doesn't offer this. Because of this, I've had to change my email.
I have been offered by Apple a partial refund for the £70 I originally paid for .Mac, but I am going to try to press for a full refund. Although I'm sure it won't come to it, I have considered legal action.
Although it looks like I've missed all the fun on the thread above, I think what some posters may have been alluding to is the fact that under EU law, consumers have the benefit of the Unfair Terms Directive which basically says that, whatever it may say in a company's terms and conditions they cannot enforce unfair terms against a consumer.
How a court would look at these, I'm not really sure. However, in general, courts are fairly sympathetic to consumers, especially when they are pitched against a global corporation. Therefore, the OP's suggestion of legal action may not be as silly as some suggest.
In realty, big corporations are usually quite pragmatic and therefore will often offer to settle a small claim rather than fighting it in the courts and incurring disproportionate legal costs.