If you're being paid for your opinion, it's not just an opinion. You can't shrug off the blame when someone follows your paid opinion by saying it was just your personal assessment of the situation. I know there are probably lawyers whose job is to write disclaimers for exactly this kind of situation, but the fact remains that a paid opinion carries more responsibility than an unpaid, unsolicited one.
Mokalus of Borg
PS - The credit rating agencies tried to call their published reports "just opinions" after the GFC.
PPS - But they knew nobody treated them as simple opinions.