Blackberry messenger pin question?

Mine is too, maybe we're special

BBM PINS are random. Some are a mixture of letter and numbers and others are all numbers or mostly letters.

As to why, I would have to guess, that when Blackberries were mostly used by corporate and government users, having 50 to 1000 employees with BBM Pins in numerical order, would make it easier to spam a large group of users at one company if you knew the PIN of just a few of the people that worked there, by spamming a large block of PIN. Making them as random, as they are, you can't spam/broadcast to a block of PINs because you don't have a starting block to go from.