Originally Posted by Rojo
Is this like the flip four heads in a row thing?
Not really. The "flip four heads" thing refers to each flip being an independent event.
What the exponential distribution has is "memorylessness", that is, it doesn't matter how long you have waited already for a certain event, the probability of it happening -from that moment on- is always the same.
I really don't know why I remember this stuff.