[H] Defrag?

[DSinc]

Can anyone please tell me why doing an EMD defrag post 'backup' is a bad 
thing?
I'd really like to understand this logic/thought.
I will allow that I do defrag (via MS) my emd devices post each 'patch 
cycle.'
Please explain.  I do accept grumble via  the MS  'defrag' logic.
Still, I use it.
Yes I am aware that many of the List disapprove of this practice. Fine.
Please tell me what I might be doing wrong?
Duncan