They have a reputation to maintain, otherwise it will be difficult to recruit the best people in future. That being said, damn, that is a very generous package by any measure.
First packages tend to be the best. If you work for them beware, the next round won't be as good (if there is one). The economy isn't the best, but if you get an okay job offer anyway you should probably take it rather than risk you will be in the next round that is worse.
True. I wasn't surprised when I was let go when my previous company had a first round. I'd clashed with management pretty openly for a while and knew if anyone had to go, I'd painted a target on myself. The people who were let go in rounds two and three were probably caught by surprise.
Dont' get it twisted, anyone; plenty of companies have a reputation to maintain for this reason (but don't do this). This is an absurdly generous severance package.