Depending on where you live you will open yourself up for at least the consequences of your own actions (negligence, errors of judgment) and possibly even for the errors of other board members because you are not only there to oversee the company, you also oversee the other board members. That's why on the spot board resignations are usually a pretty bad sign unless they are for health or other urgent personal reasons. It is a very strong signal that a board member feels that they have not been able to convince their colleagues that they are off the straight and narrow path and that their choices exceed their own thresholds for ethics or liability (or both...). And that in turn is one of the reasons why a board would normally be very upset if they feel that they have not been given all information they require to do their job and that was the very first line that the board trotted out as to why Altman was let go. But even then they should have built their case rather than just to take a snap poll at a point in time when they had a quorum to get rid of him because it seems that that and not Altman's behavior (which as far as I can see was fairly consistent from day #1) was the real reason they did what they did. In the original board (9 people) the four didn't have the vote but in the shrunk board (6) they did.