no normal person is going to think to press the Volume button, tap the middle screen, enter in a contact then hit open to get past it, lol
No need to enter a contact, just tap the volume to open an sms and youre done.
If some one just hits the volume button they may think to hit the open key.
On the other hand I agree that only someone with a jailbroken iPhone would know that so I still use android lock even though I know about the flaw.