My take on it was that people would more easily use firstbits familiar to them, possibly ones that had been previous posted on the internet. It's a bit of a heavy-handed approach, but I can't deny that users are generally stupid, and protecting them from themselves is sometimes appropriate.
Not using firstbits is already a good idea (since firstbits offer no protection against typos and practically guarantee that any mistake means you'll pay the wrong person).
But the revelation that one can see someone's identity and personal banking details by providing nothing more than a Bitcoin address and that this is by design, if true, would indicate... well... I'll leave it up to others to draw their own conclusion as to what that means.