Nick,
I agree with you that laser pens are quite harmless even at quite close range, however the lasers that are being used to target aircraft are the more powerful 'green lasers', the ones used in astronomy to point out celestial bodies. I don't know if these are any more dangerous, perhaps some one could enlighten me.
The other issue causing concern to the security forces (in my area, can't speak for others) is that Lasers can be used as rangefinders. In all probability it's kids being stupid but the possibility of terrorism cannot be discounted.
Hope this makes sense, as am in a rush to get to work.
Brom