Freesound Forums

Maybe the problem is that moderation is over-required? Not sure of the history of this, but most sites that have potential copyright problems, such as deviantArt, or SoundCloud, operate on the basis of the assumption of innocence: submissions are automatically approved, and there is a simple "flag as problematic" link on each submission, which puts it into the moderation queue.

Is there a reason that Freesound is different, and requires more rigorous moderation than the mode I described above provides?

I am not associated with the Freesound development team, but here are a few thoughts.

Different have different objectives and therefore use different models and different operating procedures. The technology behind each site is also important, as it may or may not enable certain functionalitites.

Take Youtube as a well-known example. Their model is to make money from the adverts displayed on the site, while the contents is provided by users uploading videos that others wish to see.
Youtube is rife with copyright infractions. A quick search of any big name singers will reveal hundreds of hits, often illegal video/audio recorders of ripped CD songs, video recordings at concerts/performances or even reproductions of the song videoclip.
This content usually generates a lot of hits, and Youtube is slow at removing it, while in the meantime benefiting from the views and advert hits it generates. As long as they are doing the bare minimum and eventually removing reported material, they are staying legal.

Freesound was created initially as a database to provide sounds for researchers and students working in sound processing and related areas. For example, if you wanted to test a new noise removal or audio compression algorhythm, you would want to test it in a wide range of varied audio material.
Freesound has since exceeded this initial purpose and now fulfills many roles. One of them providing amateur artists and students with free and usable audio effects for music, theater plays, school lprojects, etc.

Freesound has also been used by some big name musicians also. - So there is incentive to make sure all contents is copyright clean. Thus moderation before rather than after approval to the database.

Also, as a Moderator on this site, I feel that Freesound has an important educational role: towards users in relation to their obligations in relation to the different copyright licenses for material on this site and towards uploaders in relation to what can or can't be uploaded. Here again there is a clear benefit of pre-moderating: when there is doubt, a moderator can contact the uploader and ask some questions to clarify the copyright status of the sound. If the sound is unnaceptable it will be rejected, but the uploader will have been informed and educated about the aspects that make the sound unnaceltable.
If the sounds are already in the database, sometimes for a long period before being reported, it is then often not possible to contat the uploader anymore. Also, if the uploader realizes the sound has been flagged as copyright infringing, he/she is more likely to stay silent and avoid contact with moderators. In both cases, the chance to educate uploaders is lost.

There is also a limit in terms of quantity of material that can be pre-moderated. In that regard, obviously, Youtube could not possibly operate in this way - Even empoying an army of moderators, would be impossible to check every video to confirm if copyright OK before acepting.

Might I just add to your statement AlienXXX, which I completely agree with by the way.

We should also consider the fact that Freesound is pretty clean from irrelevant material such as songs, which are not suitable within this particular database, considering it's purpose.

If we always had an approve now moderate later system, Freesound would be very littered today.

Not to mention the myriad of text to speech spam advertising that would be inescapable.

Freesound has also been used by some big name musicians also. - So there is incentive to make sure all contents is copyright clean. Thus moderation before rather than after approval to the database.

I disagree that this style of moderation follows from that requirement, but OK. Even if you do do this, you could still have public unmoderated posts, that have a clear warning on them that the license hasn't been checked.

It's getting a bit more complex, but a gamified system like that used by StackOverflow and it's sibling sites could be useful here: Users can gain reputation points for interacting well with the site (e.g. by posting sounds/forum posts that get rated highly), and after a certain number of points, moderation access is given to the user - maybe limited at first, with more permissions as more reputation is gained. See http://stackoverflow.com/help/whats-reputation and http://stackoverflow.com/help/privileges (might need to be logged in to see the latter?).