Idiots make statements without understanding ROI. It's so freakin ign'ant to call it a scam, especially when you guys are working in a field that used to bribe ass holes to list you in DMOZ or Yahoo to get you listed in their directory (at least as much as it cost to get accredited by the BBB) which drove rankings and in turn business. The BBB drives business and also gives you a link.
In my industry, we pay for the BBB accreditation with 2 sales each year. The BBB definitely drives more than that. If it can pay for itself, you should do it, if it won't pay for itself, you shouldn't. Very simple calculation.