It can be used to debunk all the FUD posts that spring up all over this forum and other online sites whenever a large amount of bitcoin is moved. For a period of two weeks or so in December, we had at least one new topic every day posting about how "a whale" was moving 600k bitcoin, which they were definitely about to dump and bitcoin was going to crash to zero. By knowing that the addresses in question were actually Coinbase's cold storage, and they were simply moving the bitcoin from their current cold storage system to a new one, it was easy to point this out and stop the rising panic amongst all the newbies who believe everything they read at face value.
Basing your trades over whether a whale is moving funds or not has got to be the dumbest thing
Regardless, even if large funds were being moved to be sold, you'll never know until they actually are, and then of course the hindsight bias kicks in for the FUDders with the "I told you so" crap. That's even assuming a whale is stupid enough to dump a large amount over a short period of time..
So many arguments can be done against this specific sort of FUD that ranks it among the stupidest and least effective way for them to spread misinformation. Imo if big funds are being moved, it's even more of a good thing for bitcoin because it means early adopters/whales are actually active and up to date with bitcoin's protocol, and are potentially using their coins. Every transaction that moves millions of dollars around with minimal fees prove the point that you could never do the same with banks.