the feds can crack your encrypted wallets very easily. all you have to do is dump the private keys with pywallet, and save them in atext file. then you delete the wallet.dat file. rename the app data folder for bitcoin, then reinstall bitcoin. prior to launch bitcoin, move the blockchain from the old bitcoin to the new app data bitcoin folder. now start bitcoin and import the private keys. you now have an unencrypted bitcoin wallet with all the funds of the old encrypted one.
To export private keys you need the encryption passphrase. If you have the encryption passphrase you don't need to do all that nonsense you can just use the wallet.
The QT wallet uses rather robust encryption of private keys (ask anyone who forgot even part of their passphrase). The passphrase is hashed SHA-256 a few thousands times (exact number depends on computing power of the system running your wallet). This generates the 256 bit key which is used by AES for the actual encryption and decryption of the wallet. There are no backdoors and with a sufficiently complex passphrase it is beyond brute force possibility due to key hardening. Of course all of this is open source so one could just look at the source code to realize the poster is just make up garbage.