Depending on how important/inflammable this document is, I might look into buying a cheap 20GB laptop hard drive, installing ubuntu, going to a star bucks, doing the above and then "disposing" of the drive and all media so that there are no questions.
For this to work you would also have to change your wireless interface's Ethernet MAC (hardware) address. By default this is a vendor-specific code that is probably unique enough that it could be used to link you to the upload. This would require that (a) the coffee shop kept some kind of long-term logging on their wireless device, (b) the authorities were able to trace the upload to the coffee shop, and (c) the police had some kind of suspicion of you already. All are improbable, but none are impossible.
Most wireless cards will let you change the hardware address. I'll leave instructions for how to do that to the enterprising googler.
The alternative is to use a cheap throwaway laptop with wireless, or a disposable wireless ethernet card.
(Yes, it's paranoid, but so is the original question.)
Google doesn't agree:
1.0 mpg = 86 furlongs per firkin
Enterprise tape has a proven 20-year shelf life, no HDD does.
That may be, but I've lost track of the number of times (as a storage engineer) that I've seen tape backups go bad. Even "enterprise-quality" tapes. I think the claims don't match the reality.
Hard drives die too, but in the case of drive storage (1) it's a lot easier to verify your backups on a periodic basis, like every month; and (2) you can suffer a failure or two (depending on your RAID setup -- most people wouldn't run anything more than RAID-5 for backups) and react accordingly to preserve the data in full.
Of course, if you're really serious about your backups, you back up to disk and THEN offload to tapes and keep those offsite.
The legislators have thought of that. It's an infraction, rather than a misdemeanor, so it's an administrative fine -- it goes on your driving record, but not your criminal record.
Because it's a criminal charge, you aren't given the right to face your accuser.
It's a perversion of justice for the profit of the state, but right now the judges let it pass constitutional muster.
It's a naive, domestic operating system without any breeding, but I think you'll be amused by its presumption.