Quite likely if you were to actually populate every socket on the extensions with a current consuming device, or even just a few high power devices like cookers, kettles, heaters and vacuum cleaners. As long as the total of all downstream appliances connected peak power and current usages are lower than the power/current ratings (watts and amps) of the strip and any upstream extensions leads (plus their appliances), then it would be safe.
The hazard exists if you go over the rating, which can lead to blown fuses, or overheating cabling with melting insulation or melting sockets - which then becomes a fire hazard or exposed mains voltage hazard.
As put in the UK HSE guide:
"Make sure that the electrical equipment you are intending to use is suitable for the electrical supply to which you are connecting it."
References: electrical safety knowledge + experience.
UK HSE Electrical Safety Guide: http://www.hse.gov.uk/electricity/electricequip.htm