My conservative guess is 1/2 Tb and growing exponentially! I don't know where this is going to lead to. Sometimes I feel that we are at a disadvantage because the process of taking a picture has been greatly simplified and costs next to nothing. As a result, we fire off tens of thousands of photos without a moments notice.
In the film days you had to be far more methodical in what you did. There was a cost to making a mistake! I remember taking a whole roll of film and forgetting to adjust my ISO setting from a previous shoot. The photos I got back were all over-exposed!
In today's world I couldn't possibly imagine having a physical photo of every digital impression that I have on my hard drives. It would be overwhelming! It would probably take a couple hundred photo albums to store them all. And who has time to go through all those photos? I appreciate having the technology that we have today.... I would never advocate going back to the film days... but there is also a cost in the sheer numbers of photos that technology has enabled us to take.