From the instructions to the August 2005 version of the DOEP:
A bank may, but is not required to, use this form to notify the Treasury that the bank has revoked the designation of a customer as an exempt person.
If you revoke it, apparently the e-filing mechanism requires you to jump through some hoops. However, you are not required to revoke it.
My understanding is that the next iteration of the DOEP, the one reflecting the amendments to the exemption process that took effect in January, 2009, will not mention revocation at all.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.