"You should be investigated." "No, you should." That's about the gist of the latest exchanges between Bill Ackman and Herbalife (HLF -0.7%). Ackman yesterday backed a call from the National Consumers League to probe the company for possibly being a pyramid scheme. Herbalife responds by accusing Ackman of making "a reckless $1B bet against the company based on knowingly false statements."