Beyond financial regulation, I think accounting rules/regulation is a much more important area that needs to be addressed. 
areas that need to be answered
1) effects on balance sheets
2) collecting taxes
3) paying suppliers with bitcoins and being able to file as expenses

Not an accountant myself, just thinking aloud, so I figure this list is quite long.  Obviously there are cross currency accounting standards that exist that can be used as a framework.  But lets face it very few domestic businesses are ever involved with multiple currencies. But this changes as more merchants decide to accept bitcoins.   They could convert immediately to the local fiat, but this would seemingly go against the long term point of promoting bitcoin usage.

(side question - when will the spell check on the forum stop underlining in red 'bitcoin' ?)