Remember FBI is not a regulator, is law enforcement.
That is a distinction without a difference, but does not play to the issue at hand.
You hold no cards to give them. So, you can't lose anything by associating with them.
Which means the circumstance can have only:
1) nothing
2) helpful results, even if vanishingly minor
Look at it this way... When other tentacles of the great beast that is government start talking shit about DASH, you'll have this "close relationship" with the FBI... "They" can't make up bullshit, or the FBI would be on the hook for not ever having done anything about "the problem" prior. The FBI will have to cover their asses by calling out the FUD. This is the only time you can actually win against government; forcing it to call itself out. The only way "out" would be to declare the FBI hopelessly incompetent, may as well dismantle the whole agency...
So...
No possible negative because all your cards are already on the table. All you can really give them is a guided tour of what is already there.
By being friendly, you're essentially recruiting them as a future advocate by their own request... They would be in a position where they had to refute future FUD on your behalf, or look like complete fools.
My initial reaction was out of hate for their very existence... But even I can admit there are potential advantages with no possible downside...
Dipshit Politician: "DASH IS INTERNET DEVIL MONEY!!! TERRORISM! RACISM!"
DASH: "The FBI doesn't seem to think so. We've been hanging out for a while..."
That looks a lot better than
Dipshit Politician: "DASH IS INTERNET DEVIL MONEY!!! TERRORISM! RACISM!"
DASH: "Nuh UH!!! Cult of Evan is not Cult of Evan!"
With so many dipshit politicians and talking heads making asses of themselves in exactly this fashion, you could ride the "cried wolf" effect, too...
I wouldn't trust the FBI any further than I could throw it. I hate the shit out of them. I'd like to see them all get nuked. But, you don't have any cards up your sleeve... It's all open source, so what could you lose? They love to say "If you have nothing to hide..." And since you don't have anything to hide, you can play that game and still not lose...
You could even make press releases directly to them, keeping them up to date on advancements... It's totally useless, but they're the ones that asked, and it looks good...
It seems like a missed opportunity now that I think about it.