I think the implication was that you couldn't assume that one person made just one journey in a day, and therefore the figures were wrong, Sp.
However, even if you decided to work on a basis that (e.g.) every person who uses the tube makes ten journeys a day (and I imagine few would argue that the average is anything like as high) and work the figures out on that basis, the odds remain ridiculously small, and a rational person wouldn't still act upon them.
At the unrealistic 1 person=10 daily journeys, you're still more likely to die falling out of your bed than through an act of terrorism on the tube, albeit only slightly. Who is scared of getting out of their bed?
Perception of probability is absolutely subjective (though probability itself is not, which I think was what Sp was pointing out) and surely why so many people are using comparisons with more mundane forms of death to show how illogical acting on this reported fear really is.