The bull**** is certainly flying around here.
Take a look at 310-16 in the NEC and you will see that 14ga wire is really
rated at 20a. . Article 240.4(D) limits the O/C device to 15a so people who try
these "run it till it trips" experiments or lifestyles are not really creating
a hazard. If you can load a 15a breaker/14ga copper circuit enought to warm the
wire you have a defective breaker.