To answer a couple of questions so far:
1. Tom's working on the preview animation.
2. We do have a method of deleting content that violates the upload rules (e.g. copyrighted material). We just haven't started using it properly (except for one track I removed earlier today).
3. Maybe in the future, we'll add some way of users collectively deleting the content.
4. A whistle-type system does sound like a good idea.
5. No, you cannot upload someone else's material, even if it is you who's playing the track. The copyright exists on the material, not on the recording of that material. If you released a cover of one of the Beatles songs, you would have to pay royalties and ask permission from the people who take care of the Beatles' contract before even releasing it.
6. Yes, there will be an edit option in your Grounds Gold menu soon.
7. Sound effects usually have some sort of copyright on them.
8. We will probably have some sort of system to track whether or not your audio clips have been used in the Portal and notify you of them.
9. Request boxes sound like something we could use at some point in the future.
10. There is no easy way to check whether 2 sounds are the same. All of the files are stored in different subdirectories and are given unique names. Comparing filesizes isn't always a good idea.
11. Dunno about experience for voting.
12. I will add the audio listings into the profile soon. We're already cramming plenty of stuff in there - another list shouldn't hurt. :)
13. Commercial music is a threat - several users have already requested that their entries be removed from the Portal in the past because of threats from big companies.
14. Editing samples so that they sound nothing like the original is a grey area. Only get into it if you're confident that there'll be no comebacks.
15. Review writing might be put in there at some point.
Ok, I think that covers most stuff so far. :)
Remember, this is a new system and everything takes time. Have patience. And before anyone asks, no, I have not forgotten about the multi-author system. I've been playing around with some more stuff for that tonight. But it's still a long way off happening! :)