appraiser: Flexible Fees for Field Reviews - 01/27/10 04:29 AM

I was just offered a field review assignment with the fee based on whether or not I agreed upon the original appraisal. This company offered more if my opinion differed from the original report siting the additional work involved.
I can't argue with the fact that more work is involved if the review appraiser disagrees, however I find the flexible fee structure disturbing and quite non-USPAP compliant.
Wouldn't it behoove a starving appraiser to disagree with the original report simply for a few extra coins? Has anyone run into this and/or accepted an assignment?