1234 is the most common PIN used in banking.
A new study of 1100 banking customers found that 1234 and birth dates make up a large percentage of PINS. This means if your wallet is stolen, a thief can find your birth date from your license or other ID, take your ATM card and guess your PIN. And it will work for 1 in 18 stolen wallets (or 1 in 11 for some banks). They’re good odds for thieves.
The study suggests that banks issue a random PIN instead of letting you set one yourself. I think it’s a good idea. Here’s the full document.