There is a vague understanding that a partner will be classified as a general partner if the partner can:

1.  Bind the partnership to an agrement or have the authority to enter a contract on behalf of the partnership.

2.  Has personal liability for debts or obligations of partnership because he is a partner.

3.  Works over 500 hours per year.

But as is always the case, facts and circumstances determine whether a partner does in fact materially participate.  Personally I have always felt at least 1 LLC member should be judged as general, and I have often had more than that.  For instance in farm LLC partnerships where 2 brothers work the farm but both wives work in town, maybe only the 2 boys are general with wives being passive.