There are essentially 3 ways you get your idea to Apple:
-Post it everywhere. Hope they are interested, and out of good will work with you
-Get a job at Apple, then work your ideas into your projects.
-Form a company start-up, and hope Apple buys your technology and.or company
Most large companies will not even listen to suggestions. Here is why. Lets say you go to Apple and pitch your idea for the new iPod. Meanwhile, in Apple's labs, they are working on an identical product to what you suggest. Apple is in a lose-lose situation then. If they release the product, you can sue them claiming they stole your idea (which in fact they already had said idea). They cant buy the idea from you either, because they have no need for it.
Its just easy for them to have a no-solicitation policy than the legal problems raised by people suggesting things.