Zeev, (re: BIIB R&D officer) may I offer an argument for discerning a little more about the implications of resignation of an officer after merger?
In the event of mergers I have observed, it is usual that one upper management group dominates the resulting entity. This dominant group, in weeding duplicative positions, will tend to favor its own, people who were part of its pre-merger entity.
Iff one of those people, toward whom favor is prejudiced, is nevertheless deposed in favor of his/her match from the now-subordinate management group, I would take that action as a notable positive. That is, I would infer from this action that upper management has recognized either a weakness in its former management group, or a significant strength in the retained member of the merged group, and has acted accordingly.
I have not followed BIIB, IDEC or BGEN and so have no way of observing how this rule might apply in this case.
fwiw,
phill