|MadSci Network: NeuroScience|
That remindes of a "Bundy's" episode (I hope they show Bundy's in Austrailia) where the only thing Kelly knows about sports is that Al scored 4 touchdowns in the High School Championship game. Then, to compete on a TV game show, Al teaches her everything there is to know about sports. In the final round of the game show, Kelly is asked who scored the 4 touchdowns, but she can't answer becasue all the new knowledge has pushed out the only knowledge she had to start with.
Your question hits at the basics of how the brain stores memories. If, for example, the brain stored each memory "trace" in a particular neuron or at a particular synapse, then it is conceivable that there would be a limit to the amount of information that could be stored. However, recent evidence suggests that memories are stored in a "distributed" process, whereby a network of activation sequences store the profile of the memory. Some external event (perhaps a smell or a familiar sound) kind of "kick-starts" the network which then fills in the blanks - producing the stored memory. With this type of design, it is likely that there is no limit to the amount of information that can be stored, or at least the limit is several orders of magnitude greater that the "single synapse - single memory" design.
There is also a question of "recall." When we talk about memory, it is important to define what we are talking about. Memory consists of inputing information, as well as storage. Furthermore, most definitions (I believe) incorporate some mechanism for retrieval of the memory. This is the output process of "kick-starting" the network, mentioned above - or what we might say as, "I remember when ..." One drawback (maybe?) to the neural network design of memory is that filling in the blanks may not be accurate, as when many witnesses give different reports at an accident scene. Secondly, the network may require more input than the external event(s). This could manifest as the "tip-of-the-tongue" phenomenon, where you know you know (metamemrory), but you just can't spit it out.
So there are different reasons that we may be inhibited in our recall, but the way our brains are designed and function at least provides for the possibility of storing huge quantities of information. When I was in grade school, just before the microprocessor was invented, the convential wisdom was that a computer would have to be the size of the Empire State Building (or perhaps the proposed Melbourne Tower) to equal the power of the brain. I'm not sure that's so true anymore. And recently, I've heard analogies relating the brain to a hard-drive of about 100 Terabytes (100,000,000,000,000). Of course, this is all speculation.
For more information about the brain, etc. try these links
Try the links in the MadSci Library for more information on NeuroScience.