Sounds like a great business opportunity; kiosks on either side of the border where you can dump all the data from your mp3 player/hard drive, then retrieve it on the other side after your empty device has passed custom's inspections. Replace kiosk with a bus/mobile home with a fast wireless link (or even line-of-sight wifi) and you could set it up almost anywhere.

I've done this hundreds of times (as a limo driver in Seattle), and the story is accurate in that there's nobody checking IDs or the trunk of your car, they just open the heavily padlocked gate and wave you in onto the tarmac. You'll need to know the tail number of a flight arriving at that FBO within the next hour (info available online) and look presentable enough so that you don't arouse suspicions. A black suit and matching Lincoln Towncar would do the trick, and as a bonus they have huge trunks. Here's the "back door" in question.