A contributor to Forbes says she is done with allowing people to pick her brain for free. She suggests if people want to take you to coffee to pick your brain you should show them a fee schedule.
After reading Predictably Irrational I wonder if there isn't a problem from a behavioral economics perspective. One of the lessons of the book is that once money enter an exchange the feeling changes. The author Dan Ariely provides an example. If you need help changing your tire I might help you as a good person or your friend. However, if you offer me $5 to help you I might think you place no value on my time.
I think the key to building relationships and social capital is keeping the relationship like changing a tire for free. Sure at some point if people keep taking to much your time or they are using what you tell them to make lots of money you might consider charging.
Until then feel free to pick my brain, although you will probably get what you pay for.
via Twitter @justinwolfers who funny enough once picked my brain