I treat pins/pattern as a way to keep casual pranksters and nosey people out of my phone, not as a real "security measure" in the typical sense.

If I wanted actual security I would be using a full blown password and full drive encryption (both supported by Android).

But then I'd have to turn off all my toys like sync, USB debugging, and unsigned package installation. Which I don't want to do. So therefore I just take my phone being relative insecure as a given, and try to keep out the casual pranksters and or nosey people.