[fennecfoxen]

I know perfectly well that all postal-mail envelopes are recorded, yes. But I have doubts that they're intercepting all envelopes heading to Wikileaks. You can attempt to make the envelope tamper-evident, you can buy the SD card with cash at some no-name Chinatown vendor, you can drop it in the mail at any mailbox in town, and you can encrypt all the contents with the public key. This does not guarantee that your message makes it through to Wikileaks per se, but it does make it really hard to trace to you.

If you'd like, you could also identify a separate, known Wikileaks sympathizer and mail the encrypted data to them, requesting that they forward it? They could be quite brazen about it, as they are at no risk of being identified. And there are many Wikileaks sympathizers in the world; the government may be scanning their envelopes but they're not inspecting and opening all of them.