Adding myself to the list: Sudden PIP after years of being rated "exceeds", getting bonuses, equity grants, etc. Demographics-wise, caucasian, over 60.
If this happens to you (and it could, even if you don't think so!), do NOT take it personally. It is not a reflection on you, your value as a person, or your potential.
Presumably in a month or so, we will discover what life as an ex-IBM'er is like...