Anyone can get at your stuff via Xbox LIVE. If you want to export it to your PC, you'll need to do it via forzamotorsport.net. Nope, thumb drive isn't supported, but it's not due to lack of trying on our part. Trust me.
If you want to upload 720p footage of a full 2-3 minute lap or even a 7 minute lap of Nurburgring, you'll have to do it in segments since at 30 seconds the average video size is just under 50 megs or something. I need to double check. That said, you can put all of your replays (full length) on your Storefront for everyone to download and check out right off their Xbox 360. This feature is only for exporting 720p footage to your PC so you can then drop it into Final Cut Pro or Premiere and make something beautiful.
Storefronts make public to the community the following files: car liveries (the whole livery of a car), layer groups (an image or logo or whatever grouped layer you have that can be stamped anywhere and usually created using the layer group creator grid tool), photos (like you see in the pic of my storefront), tuning files for cars (our tuning community is going to love this one since tuning files can also be locked to keep that special sauce secret), and replays. Everything other than photos and replays can be sold on the Storefront with the owner controlling the inventory available until it's "sold out". You can also just put stuff up there for free. Every file type can be scored by other users and there will be a leaderboard for most popular and best rated file types, as well as a Turn 10 pick section.
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One camera "type" per video export, but that video export can be as short as 2 seconds and as long as 30. So you could be exporting short 5 second clips with various camera angles to make your video. Of course, if your camera "type" is the standard replay camera and not the other fixed camera positions, then you'll have different replay camera shots throughout your clip. If that makes sense.
The videos aren't compressed on the website. They're compressed on your Xbox 360. So there's no actual loss of quality going from 360 to the website. Putting them into a video editor, I dunno. I'll upload a sample clip from the replay exporter sometime soon. It looks damn good.