Memories of little consequence

This morning I was reading a blog where the writer was contemplating what pictures of the thousands she has to keep and archive and what to just delete. This got me to thinking: I wonder what the capacity of our brain is? A hard drive on your computer has a limited capacity for storage and I can only imagine that the brain, having a set size, has a set limit, too.

I had to google this (yes, I'm that big of a dork) and found this answer on answerbag:

"I'm not smart enough to know this off hand but this should help:

Any answer to this question should be taken with several grains of salt. Digital computers and brains don't work the same way. For one thing, every memory location in a computer is created equal. You can move stuff from one location to another without losing any information. In the brain, on the other hand, certain cells specialize in certain jobs. While there is considerable plasticity (the ability to change what some part of the brain does, enabling the brain to recover from injury), there's nothing like the uniformity seen in a computer.

Secondly, processing and memory are completely separated in a computer; not so in the brain.

Finally, data in computers is digital, and not really susceptible to "noise". In the brain, there are continuous voltages.

With those caveats, let's look at numbers. The brain contains 10^11neurons -- in other words, 100 giganeurons. Each one has synapsesconnecting it to up to 1000 other neurons. Many researchers believe thatmemories are stored as patterns of synapse strengths. If we suppose that the strength of each synapse can take on any of 256 values, then each synapse corresponds to a byte of memory. This gives a total of (very roughly) 100 terabytes for the brain.

For more info, see the book "Mind and Brain: Readings from ScientificAmerican".

Note: Please note that 1 byte = 28 bits = 256 bits with each bit
corresponding to one value for the strength of the synapse."

Only 100 terabytes in a lifetime? Thinking of all of the things that happen in your lifetime this means that your brain is obviously doing memory purging on the background process. But since we aren't actively involved in selecting memories for deletion then how are the "keepers" selected? I would think emotions or something significant would help but I have a ton of random, seemingly pointless, memories. Like splitting up the Legos with my sister, standing in a playhouse, stray moments of walking down countless streets, picking flowers at several points in my life, etc. And for that matter, how will that totally useless bit of trivia I learned at the water cooler change my other memories? Did I just forget about a flower some kid gave me in 2nd grade in order to learn that? Sad.

Any ideas on what the selection process is? What is your most pointless memory that seems to have "stuck"? Or is there something other people think you should remember that you don't?