I think that it is reasonable to expect people to use normal life skills in taking responsibility for their own safety.
It seems to be accepted knowledge that looking at the sun through a telescope (or any other optical device) can damage your eyes. Optical instruments do not routinely carry warning stickers, although manufacturers can include warnings on packaging and literature.
Warnings do seem to be commonly provided (in the public media) when there is a particular risk associated with viewing eclipses.
Of course there is always the risk of inadvertent viewing of the sun. There appear to be technical ways to ensure this cannot happen. See: http://www.freepatentsonline.com/6698904.html
It would be interesting to know whether any manufacturers of these openair “public pay” telescopes have incorporated such a device.
Ken Dodd
VSCG Administrator