My and my friend next door rather than have two dishes
on the front of our semi-detached houses (we both have 
sky plus boxes no contract but pay £10 for the HD use)
we share one dish 2 ports each any problems with this,
any interference with each othes recievers likely

Many thanks
Richard

There are no real reasons for not doing this except that to meet with
wiring regulations you must earth bond the four cables near the dish
so that even if they are disconnected from the dish, they are all
connected together and to earth.
This avoids the situation where a faulty box could potentially send
mains to the house next door.

There should be no interference problems, any more than there would be
if the receivers were in the same house.