Really? 16 weeks of salary, or 4 months of pay. In my country, you get 3 months of pay as standard when you're fired from your job. Doesn't seem that great to me to be honest.
https://en.wikipedia.org/wiki/Worker_Adjustment_and_Retraini...
When you are leaving on your own term yes.
When you are laid off you are technically still an employee for those 3 months but nowadays many companies will just tell you to not show up for security reason.
If we're laying off 20% of the company, I'd expect the package to be somewhere in the 6-12 months range. To me, that would seem more fair, considering they are completely restructuring the whole company.
In the US luckily the job market is still quite dynamic (and extremely tight by historical standards) so only in an extreme scenario would someone with Dropbox on their resume need 12 months to find another job.
They might have to take a pay cut from a 99th percentile salary to a 96th percentile salary though. Rough, I know.