In general, as an individual you should always err on the side of slightly too much paranoia, rather than too little.
(Instead we have security services engaging in idiotic security theater and individuals carelessly throwing anti-govt comments on the web, visiting the Pirate Bay and porn sites without even the most trivial precautions, like HTTPS, TOR or VMs.)

Here’s a writeup on the book if you want more details: http://swanson.github.com/writeup/2011/04/17/moonwalking-with-einstein.html

and the technique is called the Memory Palace
http://en.wikipedia.org/wiki/Memory_palace

Just fyi. Might I suggest an interview with the author of MindHacker?
http://www.amazon.com/Mindhacker-Tips-Tricks-Games-Level/dp/1118007522/ref=sr_1_1?ie=UTF8&qid=1320186740&sr=8-1

Justin was correct, most of the neurons in your brain you’ve had since birth. Your brain undergoes a huge proliferation of neurons during embryonic development and then stops making new neurons. At about six months prenatal you have created almost all of the neurons you will ever have. During your formative childhood years, your brain is highly “plastic” and capable of extensive remodeling. This remodeling is mostly the removal of unused or weak synapses as well as kill off entire neurons.

There are a few areas in your brain that continue to undergo neurogenesis (particularly olfactory bulb and the hippocampus), but many of these baby neurons tend to die before they are incorporated into active circuits.

Estimates put the human brain at around 100 billion neurons and around 100 trillion synapses. Massive parallelism =)

You were, however, correct about most of your body’s cells: much of your body is constantly growing/dieing/replacing. The brain is one of the few regions that remains fairly “static” in terms of growth and death.