The effect of dispersant in the BP oil spill?

I have been intrigued listening to discussions about the strategies BP has employed in trying to address the massive oil spill in the Gulf of Mexico. Several commentators have expressed confusion about why BP early on put tons of dispersant not only in breaking up the oil on the surface but also putting dispersant into the actual plume of oil itself before it reached the surface.  Much discussion has focused on these actions since the dispersants leave toxic byproducts and also since the use of dispersant way beneath the surface has apparently not been done before.   


While I am not knowledgeable enough to know how to weigh all the pros and cons of this chemistry issue,  one thing seems obvious to me about the non-technical implications.   When the spill is under control and the serious discussion focuses on how big a spill it is and what the liabilities might be,  the heavy use of dispersants early on will make it hard to nail down how much oil spilled and where it went.  "Out of sight out of mind" is likely to be a reality---it will be much harder to pin down blame and consequences for 'atomized' or dispersed oil which may be harder to measure and find at all.  Or whose impact may be long term.  


That, I think,  may be a real concern.