MtGOX had more than 1 million customers, but the leaked database showed that only ~70'000 were minimally active.
We don't expect Coinbase to provide more meaningful data than any other bitcoin enterprise, do we?
Impossible to know of course.
Im just relaying what was said to someone who asked, jheeze...
Since they raised 106 million from 37 VC companies who most did their due diligence we know that those numbers cannot be faked.
https://www.coinbase.com/about
Stats
1,900,000 Users
2,200,000 Wallets
38,000 Merchants
7,000 Developer Apps
No way to know how many of those 1.9 million(now 2 ) are active vs just sitting on some milibits.