Hi,
Most of the causes are bad installation, bad ventilation or people being led to believe a stove will fix a chimney with a down draught or bad up draught to begin with, I would go as far to point at the installer in the case outlined by dj01.
Many people are led to believe they can take an almost unlimited length of flue off the back spigot of the stove, the limit is 150mm.
Others are believe the stove will work as per the test certificate if fitted using flue adaptors, wrong.
Some people are fitting standard stoves in air tight rooms, mostly found in new houses, wrong the stove needs an air intake and most standard stoves are not designed to fit such an air intake.
Many so called specialist stove suppliers are vague with their answers and do not have an in house fitting service because that would mean they are responsible for both the stove and the installation.
About time our Government "Green Sector" insisted on the Hetas standards being applied to stove installations in this country because they can be extremely efficient but only when looked on as a complete package.