The only person who can withdraw coins from a wallet needs the private key (basically a long password) and most sites control that. Therefore they can disappear and take your coins. It is a risk to keep coins in a wallet that you don't fully control.
The only person who can withdraw coins from a wallet needs the private key (basically a long password) and most sites control that. Therefore they can disappear and take your coins. It is a risk to keep coins in a wallet that you don't fully control.