Regarding all that planning etc, I'd go the other way - talk is cheap and educational. Instead imagine what the "sunk costs" would be: how hard is it to do a cute little hobby prototype of the idea? Then you and a few friends goof off with it. If there's "burgeoning excitement" then you go back and do the plan for an investor.
If it's genuine friends who are talking, I'd pretty much agree here.
It's when somebody shows up out of the blue, or courtesy of somebody who's just trying to get the caller off
their phone, that I ask for a little more demonstration of thought and commitment. And definitely before I'll consent to spending a few hours of "brainstorming" (i.e. BS-ing) over a pizza.
The last person that called me had a "super idea" for something that could "revolutionize using the web on a PC." But it was important, he said, that we move
fast on it before somebody else though of it too.

His idea? Putting a
key on the keyboard that automatically added
.com after wherever the cursor was. He figured that "since we're all using the web constantly, not having to type .com all the time would be a major time saver."

Yep! That was the "super idea."

I guess he never heard about the <CTRL><ENTER> combo...

He wanted to know if I'd be interested in going in with him on a patent search...

Now you know why I ask for something more than just "an idea" before I'll waste more minutes of my life I'll never get back.