On that note, while government has been tearing down walls between agencies, in some cases we should be raising walls.
But in all seriousness, you're correct, though I temper my enthusiasm with the thought that having the walls tends to make people complacent and underestimate risks.
For example, spying on other countries is as old as governments. So maybe that's pretty reasonable, as long as we put up a wall so that those things can't be used domestically. Now that we've settled that issue, let's build some really good tools so we know what our adversaries are doing and we can always find them. Unfortunately, then the hubris of it all catches up with us when some outgoing attorney general approves massive data sharing from tools that were always understood to be permissible only because they were aimed away from us.
Until we can find some way to make our politicians respect constitutional rights, walls are frighteningly temporary.