Is it possible to access a FileVault 2 encrypted volume from Boot Camp? If I switch on FileVault 2 in Lion, can I still access my OS X volume from Boot Camp (Windows 7)? Are both volumes encrypted and decrypted together, or does it only affect the OS X volume?
And the correct answer is: No.

Encryption only affects the OS X volume. Booting into Boot Camp, the necessary password prompt to allow decryption is bypassed entirely. The volume becomes an opaque blob to anything but a running OS X system.