[BD] Blocking Foul :S

[Lewis]

Also can anyone explain this rule to me: 
"A player causes a blocking foul by taking a position that a moving opponent
will be unable to avoid and contact results." 

Does that mean I am not allowed to slow down to get my positioning to jump
for a disc if I know that the defender behind me is likely to have contact
with me? 

I really don't understand the purpose of this rule and I don't know how
people are going to interpret it at Vancouver etc
Looks like it will either get ignored or get argued over because people
don't understand it

Lewis