I'm in the brainstorming process right now, and I'll be doing this with a partner. This doesn't usually go so well.
One person will usually have "control" of the idea process, which leaves the other person to develop an idea that doesn't feel "owned" by that person. Then every time "no" is said to a further addition or subtraction from the original idea will just feel like a power play to keep the idea from being equally both people's.
This leads to resentment and bitterness, blah, blah, blah.
So...I guess trust should be there from the beginning. Also, taking elements from both partners lists and putting them together would probably be beneficial, and create better ideas.
Anyways, I've just started, but I'm already nervous. I hope this goes well.