Blockchain CEO and Cofounder Peter Smith made the claim in a tweet that also appeared to take a shot at Coinbase.

Part of me is happy after seeing/reading that tweet (I've used both services in the past and had a very bad experience with coinbase).

In my opinion this is just cheap public promotion, they may claim to adding 100k users per day - there is no way for us to know is this true.

They have a chart: Blockchain Wallet Users
- Unfortunately, it doesn't show unique users (more of a general stats).

I would think an account is equal to one user since they most likely don't allow to have multiple accounts and require identification...

You can have multiple accounts/wallets on their platform.