i can't agree with the "if its on public display its fair game" point of view, that would surely condone any work of art being public property as soon as it is released (a bit like downloading your favourite new track illegaly perhaps?).
Not at all. There's a huge diff between what's on the net and what's in Museums and Art Galleries. Let's put it another way. I go to a city and go sightseeing. I visit a museum or an art gallery. I go home and tell my family and friends about it. Ho-Hum.

Same scenario but this time I take my trusty Nikon. I go home and Oh WOW! My family and friends suddenly want to go and visit those same museums etc.

Trouble is, those in charge think me and my Nikon are out to rip somebody / them / the artist off. I can't beleive that every tourist is a rip-off artist.
As Quest said, they should be gratefull for the free publicity.
But it seems that with St Pauls the aim is to force you to buy THEIR photographs.

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All the Woes of a World by Jonathan Icknield aka The Bryster

And in my final hours - I would cling rather to the tattooed hand of kindness - than the unblemished hand of hate...