opes and technology picks

> By appearing to make it legitimate (as RFC 1918 made NAT appear
> legitimate). There is a possible way to deal with this though: require an
> OPES box to obtain explicit consent from both ends before executing
> any content manipulation. 
>
>   Brian
Why is it not acceptable to have one host or its owner approve of such a 
use?  Consider a web farm.  How do we decide whether such "legitimate" 
uses will be outweighed by "illegitimate" uses?
Eliot