I guess one key difference is that unlike FB, DARPA money doesn't need to be confined to make quick and visible returns, thus they can focus on more long term problems.
[1] https://www.macrotrends.net/stocks/charts/FB/facebook/resear...
It's a near & dear book to me (although due for a re-read at this point), & I think many others. A history of many of the ideas circulating, and how many overlapped & reinforced on the way to building what ended up being the internet. There's more internet-centric accounts like Where Wizards Stay Up Late or Dealers of Lightning, but Dream Machines remains the favorite of many[2].
I just cant emphasize enough how much benefit I think there is to government granting good hard working big idea people, with not a lot of oversight or expectations. The counter though, is that these were relatively small organizations, all in all, and the goal is not to create jobs for life (as I feel like most other research institutions tend to do) but to fund projects, ideas, for a duration, and then move on, re-allocate funds.
[1] https://www.wired.com/2001/10/the-dream-machine-j-c-r-lickli...
For instance, at every company I've worked at, all of the infrastructure is under the R&D budget.
Like in the last two years, quite a lot of software developers in Poland suddenly started doing "R&D", because performing the necessary rituals to convince the tax man that your CRUD app is "research" let you drop your tax rate to 5%.
There's nothing secret about it.
Moreover, many US corporations are effectively encouraged by tax law to go into debt (and always operated under debt), because having a zero effective income means you pay zero taxes. So that's what many companies -- they spend a little bit (or sometime a lot) more than their revenue, and thus report a loss each year (consequently paying zero taxes).
DARPA doesn't actually do much (any?) research on its own. Its role is to award contracts to "performers" that actually run the experiments, train the models, build the devices, etc.
In other words, a big chunk of (e.g.,) Teledyne's R&D budget is actually the same money as DARPA's R&D budget.
Source: was at BBN while DARPA pushed the Internet and created SIMNET. Did work for DARPA at own company later. Never met a wooly-haired, wild-eyed fellow nerd or VC with half the imagination of buzz-cut DARPA people.