At what point is an ffl license requried?

I buy and sell guns every now and then.. as many people do without an ffl license. I'm just wondering what requires an ffl license other than receiving shipped guns.

This was debated here a few weeks ago. The answer is, "There is no answer."

Like some other ATF regulations, the answer lies in the mind of the ATF. ATF likes to scare folks into complying with their restrictive concept of the regulations. And apparently they have started attending gun shows to threaten private sellers.

I'll see if I can find the link to the previous discussions and post it.

ETA: Here you go. This gets into what you are asking about:

http://www.msgunowners.com/t17582-atf-and-the-non-dealer