I know this is little bit old but I can confirm this. I already posted this in the german section.

Its like in the quote. If you have more money they will take rest of the money. I don't know why they do this.

I would say "Ok" if I have $15  balance and I pay 5 and they take 7.. but no they take all.. so they took $10 for the payment of $5.
In my opionen they "failed" in their fee calculation.

And why I can confirm it? I paid from coinbase to block.io and the fee was low. I used block.io API to start a mass payment to multiple address in ONE transaction. My fee preview showed me its under $2 (thats the API from block.io). Then I started to pay it. And suddently its rest of the btc gone. Yep block.io said $2 first and then they took all of the money for "fee" . I couldn't pay other customers because of this.

I do this since few month in the week multiple times. Suddently they started to take all of the balances.

I tried to contact them too but they do not reply. I was really going to pay the developer planging price of $99. So I am glad I didn't pay that.
Well I will never use block.io again.

I will just use software wallet - like the bitcoin-qt / bitcoind and make my own api on our server.