As everyone knows daisy-chaining power strips is very bad and dangerous. But could someone tell me why it's dangerous from a physics standpoint? (i.e. its effect on voltage, current, etc)
"Daisy-chaining" together power outlet strips is dangerous because it provides so many outlets into which electrical appliances can be plugged that it becomes easy to exceed the current-carrying capacity of the outlet strip(s) nearest the beginning of the chain. This can cause those strips to overheat, melt, and catch fire.
Is it not more of a problem with unfused (or improperly fused) strips and adaptors?
Or strips that are poorly designed with the assumption that the load presented at any one socket will be a certain fraction of the overall fused load which the strip is able to cope with? And therefore placing a high load on a single socket will not blow the fuse, but will put undue strain on the internal bus - especially if you use the socket furthest from the supply cord.
No strip can tell whether the load presented to it is presented by an appliance directly, or by another strip - so any danger is essentially an inherent and designed-in vulnerability to high loads.
Daisy-chaining a series of strips which serve patently low-power devices is perfectly safe.
Incidentally, there is also the problem that extension reels will be designed on an assumption about the amount of heat dissipated when the reel is uncoiled. If the reel remains coiled, the safe capacity drops dramatically (typically to less than half).
There is also the problem of voltage drop over long, high-resistance lines, causing devices to malfunction if they are operated outside their rated voltage and typically to consume a greater current.