It's a good idea, of course, to set a PIN code for your phone in case it's lost or stolen. But you have to wonder why some people bother - because, according to one software developer, the most common choice is 1234.
Daniel Amitay created an app called Big brother Camera Security, which takes a photo of anyone using the customer's phone, and which now also phones home anonymously with the chosen PIN code.
And, he says, some people are awfully unimaginative. The top choice, 1234, was picked by 4.3 percent of users; and 0000 by 2.6 percent. Next came 2580, 1111, 5555 and 5683.
The top ten codes, says Amitay, account for 15 percent of all passcodes in use.
While 2580 may not be obvious, it runs straight down the phone keyboard; 0852, the seventh most popular choice, runs the other way.
"Most of the top passcodes follow typical formulas, such as four identical digits, moving in a line up/down the pad, repetition," he says.
"5683 is the passcode with the least obvious pattern, but it turns out that it is the number representation of LOVE (5683), once again mimicking a very common internet password: 'iloveyou'."
Amitay suggests - rather plausibly - that because his app's password setup and lock screen are very simiar to the actual iPhone lock screen, many people will be using the same number for both.
And Graham Cluley of security firm Sophos has one more point to make: "What's the four-digit PIN you use at the bank's ATM cash machine?"