Cheers Rob - tbh I'm still learning about optics as they're not my strong point
In my quest to better understand I've found a couple of interesting sites - there's this calculator
which is useful for understanding about the relationship between the focal lengths of telescopes, their eyepieces and resultant FOV and magnification.
The wikipedia page on telescopic sights
also gives a decent overview of the relationship between the optical parameters involved in a 'scope. It's interesting to note that eye relief is apparently dependent on focal length (which I didn't know before I read the page).
I think your point about high mag 'scopes raises two interesting points - a) again the different requirements of different user groups, and unfortunately b) that potentially marketing men are happy giving uninformed customers what they want rather than what everyone might actually need..
In other news I appreciate your Reznor / Cash reference