Block ID's / Defrag

I just discovered that on Friday someone from networking installed defrag software on our SQL servers.
I know for a fact that Oracle stores block information internally, so if this defrag software moves an Oracle database file, it'll crash the server (assuming it can move it - oracle may have it locked and prevent the move).
Does SQL server not do the same thing? Can I not expect SQL to crash any time??
The defrag program is Diskeeper2009..
An email would be appreciated as well as the post for others to view
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Brian

I don't know about Diskeeper2009, but recently I hung up SQL server (2000) with JkDefrag.SQL services could not be stopped, nor could server be softly restarted ( for more than 30 minutes ).I suspect the problem is when it relocates a .MDF file that has a large fragment.It appears that that portion of the file becomes locked during the move, which for say a 10GB fragment could be a significant period of time.I have used contig (Sysinternals) to defragment individual MDF files without problem, but that may have been because on the first pass the file was in small fragments.So be careful, or your users may be unhappy.