Every year the Florida Bar asks me to tell it the number of hours of pro bono work I did in the past year. I am not required to do any, but I have to report those hours that I did. Since joining the Bar in '87, I have a grand total of zero hours of pro bono work. I have always felt a little guilty about it (but since I am not really practicing law--I worried about not really being up to the challenge), but now I don't feel so guilty thanks to Ted Frank's description of the potential costs of jury trial lasting nine months regarding an $800 dispute.
I do recognize that there may be some worthy pro bono cases (where the social benefits are greater than the social opportunity costs and not all pro bono services involve litigation), but perhaps the incentives to provide the free work (training for litigators, feeling good, or looking good on reports) are geared towards over provision of free services. If so, we are imposing more on society in terms of opportunity costs than the cases themselves are really worth. This looks like a good dissertation topic too.