Hei Rowland i do agree your comment on co-marketing concept and partnership. Here i raise my opinion what i have understood and found (im not raise my case SO any objection overruled hehehhe) . My fellow friends I feel that there are several advantages may obtained from both(co-marketing and partnership) such as :

1. Collaboration.
2. tax advantages
   
3. flexibility
4. acquisition of capital
5. and of course law uniform BUT i think we should consider the drawback also.....

while collaborating with partners can be great advantage for small scale business but sooner or later conflict with partner may occur in big decision making. When one partner signs a contract, each of the other partners is legally bound to fulfill it, or another word is authority of partner . other disadvantages are limitations on transfer of ownership and unlimited liability.
Anyway, choosing a partner is one of important elements before forming partnership...

Just an opinion....correct me if im wrong hehehhehe