If you have extremely critical information on a crash hard disk,
then professional recovery services are definitely the way to go.  In
our situation, we had backups that were about 3 weeks old.  There would
have been significant data loss, but nothing that couldn't be
considered acceptable loss or regenerated by hand or from paper.

Also,
the recovery method I used did not attempt to write to the damaged hard
disk at all.  The dd command simply attempts to read and copy what
bytes could be successfully read to another disk.  The only risk would
be if the disk went abnormally haywire and starting writing garbage to
the disk.  However, this is extremely unlikely.  This is different than
copying data from a mounted partition which could possibly cause writes
to a occur on the disk due to file access times being updated.  That
method on a damaged disk is definitely more risky.